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From  the  collection  of  the 

o  Prejinger 

v    IJibrary 

San  Francisco,  California 

VOL.  XX  NO.  : 




JANUARY,  1933 


The  Society  of  Motion  Picture  Engineers 

Its  Aims  and  Accomplishments 

The  Society  was  founded  in  1916,  its  purpose  as  expressed  in  its 
constitution  being  "advancement  in  the  theory  and  practice  of  mo- 
tion picture  engineering  and  the  allied  arts  and  sciences,  the  standardi- 
zation of  the  mechanisms  and  practices  employed  therein,  and  the 
maintenance  of  a  high  professional  standing  among  its  members." 

The  Society  is  composed  of  the  best  technical  experts  in  the  various 
research  laboratories  and  other  engineering  branches  of  the  industry 
in  the  country,  as  well  as  executives  in  the  manufacturing  and  produc- 
ing ends  of  the  business.  The  commercial  interests  also  are  repre- 
sented by  associate  membership  in  the  Society. 

The  Society  holds  two  conventions  a  year,  one  in  the  spring  and  one 
in  the  fall.  The  meetings  are  generally  of  four  days'  duration  each, 
and  are  held  at  various  places.  At  these  meetings  papers  are  pre- 
sented and  discussed  on  all  phases  of  the  industry,  theoretical,  techni- 
cal, and  practical.  Demonstrations  of  new  equipment  and  methods 
are  often  given.  A  wide  range  of  subjects  is  covered,  and  many  of  the 
authors  are  the  highest  authorities  in  their  distinctive  lines. 

Papers  presented  at  conventions,  together  with  contributed  arti- 
cles, translations  and  reprints,  abstracts  and  abridgments,  and  other 
material  of  interest  to  the  motion  picture  engineer  are  published  in 
the  JOURNAL  of  the  Society. 

The  publications  of  the  Society  constitute  the  most  complete  exist- 
ing technical  library  for  the  motion  picture  industry. 




Volume  XX  JANUARY,  1933  Number  1 



The  Problem  of  Motion  Picture  Projection  from  Continuously 
Moving  Film F.  TUTTLE  AND  C.  D.  REID  3 

Wide  Screen  Photography  with  Cylindrical  Anamorphosing 
Systems  and  Characteristics  of  Motion  Picture  Lenses  and 
Images H.  S.  NEWCOMER  31 

Photographic  Effects  Obtained  with  Infra  D  Negative 

D.  R.  WHITE       54 

"narks  on  the  Making  of  Sound  Records  on  Lenticular  Color 
1ms A.  P.  RICHARD      60 

ing  a  Fade-Out  by  After  Treatment 

C.   E.   IVES,  L.   E.  MUEHLER,  AND  J.  I.  CRABTREE         65 

ical  Problems  in  the  Recording  and  Reproduction  of  Music 
for  Motion  Pictures D.  MENDOZA      79 

New  Apparatus 84 

Book  Review 88 

Officers 89 

Society  Announcements 90 





Board  of  Editors 

J.  I.  CRABTREE,  Chairman 



Published  monthly  at  Easton,  Pa.,  by  the  Society  of  Motion  Picture  Engineers. 

Publication  Office,  20th  &  Northampton  Sts.,  Easton,  Pa. 
General  and  Editorial  Office,  33  West  42nd  St.,  New  York,  N.  Y. 

Copyrighted,  1933,  by  the  Society  of  Motion  Picture  Engineers,  Inc. 

Subscription  to  non-members,  $12.00  per  annum;  to  members,  $9.00  per  annum, 
included  in  their  annual  membership  dues;  single  copies,  $1.50.  A  discount 
on  subscriptions  or  single  copies  of  15  per  cent  is  allowed  to  accredited  agencies. 
Order  from  the  Society  of  Motion  Picture  Engineers,  Inc.,  20th  and  Northampton 
Sts.,  Easton,  Pa.,  or  33  W.  42nd  St.,  New  York,  N.  Y. 

Papers  appearing  in  this  Journal  may  be  reprinted,  abstracted,  or  abridged 
provided  credit  is  given  to  the  Journal  of  the  Society  of  Motion  Picture  Engineers 
and  to  the  author,  or  authors,  of  the  papers  in  question. 

The  Society  is  not  responsible  for  statements  made  by  authors. 

Entered  as  second  class  matter  January  15,  1930,  at  the  Post  Office  at  Easton, 
Pa.,  under  the  Act  of  March  3,  1879. 



Summary. — The  advantages  claimed  for  non-intermittent  projectors  are  presented, 
followed  by  a  list  of  questions  that  the  writers  think  should  be  answered  with  regard 
to  any  projector  of  this  type.  The  various  projector  types  are  then  classified  ac- 
cording to  the  optical  means  used  to  form  a  fixed  image.  Two  types  of  error  are 
noted  and  each  type  of  projector  listed  is  discussed,  keeping  these  in  mind.  A  reference 
table  is  appended  to  serve  as  a  rapid  review. 

It  has  been  the  privilege  of  the  authors  to  review  the  several 
hundred  patents  which  have  been  granted  on  non-intermittent  mo- 
tion picture  projectors.  We  have  found  that  the  problem  of  producing 
a  satisfactory  screen  image  from  moving  film  by  means  of  moving 
optical  parts  is  not  a  simple  one,  and  it  seems  desirable  to  discuss  the 
difficulties  encountered  in  the  design  of  the  several  types  of  such 

Since  any  non-intermittent  projector  would  have  to  compete  with 
the  intermittent  machine,  and  since  the  optics  of  the  former  ad- 
mittedly will  have  to  be  more  complicated,  we  must  consider  what 
offsetting  advantages  may  be  possessed  by  the  non-intermittent 

A  summary  of  the  advantages  claimed  follows: 

(1).  There  might  be  less  wear  and  tear  on  film  which  is  pulled  at  a 
constant  linear  velocity  through  a  machine  than  on  film  which  is  inter- 
mittently accelerated  by  a  machine. 

(2) .  There  would  probably  be  less  difficulty  in  running  film  already 
damaged  through  a  non-intermittent  machine.  With  the  intermittent 
projector,  a  few  successive  damaged  perforations  cause  the  loss  of  the 
loop,  and  further  damage  to  the  perforations  until  the  loop  is  restored. 
The  non-intermittent  machine  will  usually  restore  itself  to  a  running 
condition  even  though  the  film  be  damaged  over  a  considerable 

*  Reprinted  from  /.  Opt.  Soc.  of  America,  22  (Feb.,  1932),  No.  2,  p.  39. 
**  Eastman  Kodak  Co.,  Rochester,  N.  Y. 

4  F.  TUTTLE  AND  C.  D.  REID  [J.  S.  M.  P.  E. 

(3).  There  is  a  possibility  that  there  might  be  more  total  light  to 
the  screen,  since  no  shutter  is  needed  to  cover  up  the  movement  of  the 

(4).  There  might  be  a  better  portrayal  of  action  if  each  picture  is 
allowed  to  blend  into  the  successive  picture. 

(5).  If  the  light  to  the  screen  can  be  kept  constant  at  all  times 
during  the  projection  cycle,  it  may  be  possible  to  eliminate  flicker 
entirely.  Some  inventors  have  argued  that  the  interruptions  of  the 
light,  even  though  of  frequencies  high  enough  to  eliminate  visible 
flicker,  cause  some  eye-strain. 

(6) .  The  ideal  non-intermittent  machine  might  be  much  less  noisy. 
In  the  present  intermittent  machine,  certainly  a  large  part  of  the 
noise  comes  from  the  intermittent  pull-down  and  from  the  film  moving 
intermittently  in  the  loops  and  through  the  gate. 

(7) .  There  might  be  less  trouble  with  wear  in  the  non-intermittent 
machine.  In  the  intermittent  machine,  wear  in  the  pull-down  parts 
causes  unsteadiness. 

(8).  In  a  portable  sound-on-film  projector,  there  might  be  a 
number  of  mechanical  advantages  in  not  having  to  have  the  film 
moving  intermittently  at  the  picture  aperture  and  continuously  at 
the  sound  gate. 

None  of  these  possible  advantages  is  great  enough  to  offset  any 
serious  imperfections  in  the  projected  picture,  such  as  unsteadiness, 
distortion,  and  poor  definition.  This  does  not  mean  that  we  would  be 
right  in  insisting  on  theoretical  perfection  in  the  projected  picture. 
Practically  every  non-intermittent  machine  involves  approximations, 
and  in  studying  these  machines  we  have  found  it  desirable  to  set  up 
more  or  less  arbitrary  standards  for  theoretical  steadiness,  distortion, 
and  definition.  If  we  make  these  standards  about  equivalent  to  the 
practical  standards  of  the  intermittent  machine,  we  could  allow  about 
the  following  approximations: 

(1).  Steadiness  of  the  center  part  of  the  picture  plus  or  minus 
0.0005  inch  (referred  to  the  film  frame). 

(2) .  Distortion  movement  in  the  corners  of  the  frame  plus  or  minus 
0.001  inch. 

(3).     Definition. 

(a) .     In  the  center  of  the  frame  0.001  inch  (circle  of  confusion) . 
(b).     In  the  corners  0.002  inch. 

With  intermittent  equipment,  considering  the  errors  in  the  camera, 


the  printer,  and  the  projector,  we  are  fortunate  if  successive  frames 
are  registered  in  the  projector  gate  closer  than  plus  or  minus  0.0005 
inch,  which  makes  our  steadiness  tolerance  seem  reasonable.  Twice 
the  movement  has  been  allowed  in  the  corners  of  the  frame  that  was 
thought  permissible  for  the  center  of  the  frame,  because  of  the  belief 
that  the  eye  is  not  particularly  concerned  with  movement  away  from 
the  center  of  interest.  The  definition  tolerances  used  here  are 
equivalent  to  those  usually  found  in  practice  in  motion  picture  work. 
With  regard  to  definition,  it  has  been  observed  that  if  the  definition 
is  poor  during  some  parts  of  the  projection  period,  but  good  during 
other  parts  of  the  projection  period,  the  eye  sees  definition  that 
is  somewhat  better  than  the  arithmetical  time  average  of  the  defi- 

Before  listing  the  different  classes  of  non-intermittent  projectors 
and  outlining  the  difficulties  encountered  in  their  design,  the  following 
questions  are  presented  as  those  which  we  think  should  be  answered 
with  regard  to  any  of  these  projectors. 


(1).  Is  the  center  point  of  the  picture  stationary  within  sensible 

(2).  Does  distortion  give  a  "rubbery"  effect  in  the  picture,  or 
does  it  make  corner  definition  too  poor  to  be  acceptable? 

(3).  Is  the  definition  in  the  picture  comparable  with  intermittent 

(4).  Is  the  picture  made  flat  by  flare  from  many  free  glass-air 
surfaces  ? 

(5) .  Does  the  system  permit  of  fading  out  of  one  picture  into  the 


(6).  Does  the  system  impose  limitations  on  the/  aperture  of  the 
projection  lenses? 

(7).  Is  the  light  lost  by  passing  through  many  surfaces  or  from 
reflections  serious? 

(8).  Is  the  light  to  the  screen  during  the  change-over  period  equal 
to  the  light  when  projecting  wholly  from  a  single  frame,  or  is  it  neces- 
sary to  introduce  diaphragms  or  shutters  which  cut  down  on  the 

(9).     Does  the  system  require  a  special  moving  condenser  system? 

6  F.  TUTTLE  AND  C.  D.  REID  [J.  S.  M.  P.  E. 


(10).  If  cams  are  used,  what  is  the  precision  required  in  cutting 
the  cam?  Are  the  surfaces  such  that  they  can  be  cut  with  precision 
from  point  to  point? 

(11).  What  precision  is  required  in  the  gear  trains  connecting  film 
drive  with  optical  displacement  means? 

(12).  What  precision  is  required  in  the  sprocket  exactly  fitting 
the  film?  Is  a  jump  back  as  one  tooth  leaves  a  perforation  and  the 
next  tooth  starts  to  drive  serious? 

(13).     What  precision  is  required  in  initial  adjustment? 

(14).  What  precision  is  required  in  the  making  or  matching  of 
optical  parts? 


(15).  Does  the  system  impose  impractical  limitations  on  the 
equivalent  focus  or  the  back  focus  of  lenses? 

(16).  Does  the  system  demand  ridiculous  physical  dimensions 
in  the  projector? 

(17) .  Does  the  system  necessitate  a  fixed  screen  distance  or  a  fixed 

(18).  Is  the  system  capable  of  projecting  lenticulated  color  film? 

(19).  Is  a  special  arrangement  of  pictures  on  the  film  or  a  special 
type  of  film  assumed? 

(20) .     What  type  of  framing  device  is  required  ? 


(21).  Are  all  moving  parts  moving  with  constant  angular  velocity 
and  can  all  of  them  be  counterbalanced? 

(22).  How  does  the  mass  and  moment  of  inertia  of  reciprocating 
parts  compare  with  the  mass  and  moment  of  inertia  of  the  inter- 
mittent projector  parts? 


(23).  Is  it  necessary  to  use  simple  lenses  of  large  /  apertures 
covering  large  fields? 

(24) .  Is  it  assumed  that  a  single  image-forming  reflector  working 
with  a  large  aperture  will  cover  a  considerable  field? 

(25) .  Is  it  necessary  to  assume  that  a  warped  reflecting  or  refract- 
ing optical  part  can  be  made  with  great  precision? 

(26).  Does  the  system  demand  the  use  of  large  aperture  crossed 
cylindrical  lenses  to  work  as  a  well  corrected  spherical  lens? 



It  is  conceivable  that  any  device  for  refracting  or  reflecting  light 
might  be  used  to  give  an  optical  displacement  to  an  image  which 
ould  compensate  for  the  movement  of  the  film.     The  following 
ist  indicates  the  elements  which  have  been  used,  with  a  very  short 
description  of  how  they  were  moved. 

Moving  Lenses 

Reciprocating  lens 

Linear  motion  of  lenses  in  restricted  path 

Circular  motion  (optical  axes  describing  cylinder) 

Circular  motion  (optical  axes  radial) 

Circular  motion  of  cylindrical  lenses 
Plane  Parallel  Plates 

Uniformly  rotating  cube  or  hexagonal  prism 

Cam  rotated  plate 

Uniformly  rotating  plate  with  normal  to  the  plate  describing  a  cone 
Refracting  Prisms 

Cam  actuated  variable  angle  liquid  prism 

Uniformly  rotating  warped  refracting  elements 

Equal  prisms,  cam  rotated  equally  and  oppositely 
Reflecting  Plane  Mirrors 

Cam  reciprocated  mirror 

Cam  actuated  series  of  mirrors 

Uniform  rotating  drum  of  mirrors 

Helical  reflecting  surfaces 

Rotating  rhombs 

Moving  right  angle  reflectors 
Skewed  Image  Forming  Elements 

Concave  spiraled  mirror 

Spiraled  lens 

In  the  discussion  of  these  displacement  means,  we  would  like  to 
point  out  two  types  of  errors  that  occur: 

(1) .     Errors  that  are  inherent  in  the  displacement  means  employed. 

(2).  Errors  that  result  from  the  method  used  in  moving  the  dis- 
placement means. 


Perfect  lenses  can  be  moved  theoretically  in  such  a  manner  that 
there  is  no  inherent  defect  in  the  displaced  image  produced.  In  prac- 
tice the  means  of  moving  the  lenses  and  the  use  of  simple  lenses  intro- 
duce difficulties. 

If  we  move  a  lens,  as  in  Fig.  1,  in  such  a  way  that  a  straight  line  at 
all  times  passes  through  the  center  of  the  picture  frame,  the  center  of 
the  lens  and  the  center  of  the  screen,  we  will  have  a  stationary  image 



[J.  S.  M.  P.  E. 

on  the  screen  from  film  which  is  moving.  We  can  design  a  cam  which 
will  reciprocate  a  single  lens  in  this  manner,  but  we  must  have  a 
shutter  which  will  cover  up  the  return  of  the  lens,  and  must  introduce 
flicker  blades  which  will  give  high-frequency  interruptions.  Further, 
the  cam  would  have  to  be  accurate  to  plus  or  minus  0.0005  inch. 
The  mass  we  are  accelerating  in  such  a  system  is  larger  than  in  an 




FIG.  1.     Optical  compensation  for  film  motion  by  a  single  moving  lens. 

intermittent  projector,  and  the  same  aperture  lens  can  not  give  the 
same  amount  of  light  to  the  screen  without  a  larger  source  or  a  moving 
condenser  system. 

Our  first  attempt  at  improvement  on  this  system  probably  would  be 
to  try  to  have  a  series  of  lenses  moving  in  a  straight  path  in  front  of 
the  film  so  spaced  that  when  one  lens  is  following  one  frame  from 



FIG.  2.    Optical  compensation  for  film  motion  by  a  plurality  of  moving  lenses. 

the  top  to  the  bottom  of  a  two-frame  aperture,  the  next  lens  is  ready  to 
follow  the  next  frame.  This  system  would  allow  us  to  do  without  the 
shutter  for  covering  the  return  of  the  lens.  It  would  be  very  difficult, 
however,  to  keep  the  light  to  the  screen  constant  as  we  change  from 
one  frame  to  the  next,  and  we  would  very  likely  end  up  with  some  type 
of  shutter  or  diaphragm  in  the  system  which  would  reduce  the  light. 


With  two  lenses  in  the  position  shown  in  Fig.  2,  we  can  see  that  the 
physical  diameter  of  the  lenses  is  limited  to  a  little  less  than  the 
height  of  the  frame.  If  the  lens  has  a  focal  length  long  enough  to 
cover  the  frame  satisfactorily,  we  find  that  this  limits  the  /  aperture 


LENS        ' 


FIG.  3.     Optical  compensation  for  film  motion  by  a  plurality  of  moving  lenses 
and  a  fixed  lens  forming  a  virtual  image  of  moving  film. 

to  a  maximum  of  something  like  //4,  if  we  allow  a  minimum  of  lost 
space  for  the  mount. 

We  can  gain  considerably  in  the  aperture  of  the  system  if  we  use 
the  arrangement  shown  in  Fig.  3.     A  stationary  lens  subtending  an 

FIG.  4.  One  type  of  con- 
stricted path  to  give  a  linear 
motion  to  the  moving  lenses. 

f/2  angle  forms  an  enlarged  virtual  image  of  the  film  and  the  moving 
lenses  move  so  that  a  straight  line  connects  the  center  of  the  virtual 
image,  the  center  of  the  moving  lens,  and  the  center  of  the  screen. 
With  16-mm.  film  projected  with  the  equivalent  of  a  2  inch  lens,  we 



[J.  S.  M.  P.  E. 

can  have//2  light  to  the  screen  at  all  times  using  moving  lens  elements 
which  have  apertures  of  only  about  //6.  With  this  system  the  ratio 
of  the  physical  diameter  of  the  moving  element  to  the  diameter  of  the 
stationary  lens  will  determine  the  manner  in  which  we  may  fade  out 

FIG.  5.    Two  wheels  of  lenses  used  to  avoid  the  horizontal  displacement 
produced  by  a  single  wheel. 

of  one  picture  into  the  next.  If  the  diameter  of  the  moving  element 
is  equal  to  the  diameter  of  the  stationary  element,  we  will  be  con- 
stantly changing  from  one  picture  to  the  next.  If  the  diameter  of 
the  moving  element  is  much  larger  than  the  diameter  of  the  stationary 
lens,  we  may  divide  the  projection  cycle  so  that  during  only  half  the 
time  we  are  fading  out  from  one  picture  to  the  next. 



FIG.  6.    Optical  diagram  showing  the  paths  of  rays  through  the  double  wheel  of 


With  35-mm.  film  projected  with  the  equivalent  of  a  5-inch  lens, 
we  can  get//2  light  again  by  using //6  elements.  With  either  film, 
if  we  can  afford  to  increase  the  equivalent  focus  of  the  projection 
system,  we  can  use  moving  elements  which  have  smaller  /  apertures 

Jan.,  1933]         CONTINUOUSLY  MOVING  FlLM  PROJECTION  11 

and  have  to  cover  smaller  angular  fields.  Thus,  we  see  that  it  may 
become  possible  for  us  to  use  comparatively  simple  moving  lenses 
which  is  much  better  than  having  to  use  and  to  move  a  lot  of  well 
corrected  lenses. 

Other  arrangements  of  a  moving-lens  optical  system  are  possible. 
The  moving  lenses  working  on  real  or  virtual  objects  can  be  used  to 
form  stationary  real  or  virtual  images.  It  is  possible  also  to  consider 
negative  lenses  in  some  cases  for  the  moving  lenses.  Detailed  dis- 
cussion of  all  types  is  beyond  the  scope  of  this  paper. 

The  problem  of  moving  lenses  in  a  straight  path  at  a  constant  linear 
speed  past  the  gate  is  not  very  easily  solved  mechanically.  Several 
inventors  have  shown  lenses  in  a  belt  which  move  in  a  restricted 
path  as  shown  in  Fig.  4,  with  the  lenses  either  linked  together  or 
crowding  each  other  along  in  a  channel  with  a  drive  for  the  lenses 
supplied  at  some  circular  part  of  the  path  by  some  kind  of  rotating 
sprocket.  Such  a  system,  however,  is  usually  noisy  and  inconvenient. 

Fig.  5  shows  the  lenses  arranged  about  a  wheel.  A  single  wheel 
would  give  the  lenses  an  undesired  horizontal  displacement  equal  to 
the  sagitta  of  the  arc  over  which  the  lens  is  used.  The  optical  effect 
of  the  horizontal  displacement  can  be  offset,  however,  if  a  similar 
wheel  of  lenses  rotating  about  another  axis  is  used  as  shown  in  Fig.  5. 
Fig.  6  is  a  top  view  of  the  lenses  arranged  in  two  wheels,  showing  how 
the  horizontal  displacements  of  the  two  lenses  are  opposite;  they 
can  be  made  to  give  zero  optical  displacement,  if  the  focal  length  and 
the  magnification  for  each  lens  are  correct.  The  vertical  component  of 
the  displacement  varies  as  the  sine  of  the  angle  through  which  the 
lens  wheel  is  rotated.  If  we  turn  the  wheels  at  a  constant  angular 
velocity,  we  will  find  it  necessary  then  to  have  the  film  pass  over  a 
curved  gate,  if  we  insist  that  the  image  of  the  center  point  of  the 
frame  be  made  exactly  stationary  on  the  screen.  The  use  of  this 
curved  gate,  however,  will  introduce  distortion  in  the  picture.  By 
making  a  compromise  between  distortion  and  steadiness,  satisfactory 
projection  can  be  obtained  with  the  system  described  if  the  two 
wheels  used  each  contain  a  sufficient  number  of  lenses. 

Fig.  7  shows  another  arrangement  of  lenses  in  a  wheel.  This 
arrangement  of  lenses,  when  used  with  a  straight  gate,  will  give  un- 
desirable keystoning  of  the  image  on  the  screen,  since  all  parts  of  the 
film  are  not  the  same  distance  from  the  plane  of  the  lens.  Even  a 
curved  gate  will  not  rid  us  of  this  defect  for  the  image  plane  is  not 
fixed.  Fig.  8  shows  the  way  the  image  surface  shifts  with  respect 



[J.  S.  M.  P.  E. 

to  the  screen.     However,  if  enough  lenses  are  used  in  the  wheel, 
satisfactory  projection  can  be  achieved. 

The  problem  of  moving  cylindrical  lenses  in  such  a  manner  that 
the  image  will  appear  stationary  is  not  as  difficult  as  is  the  problem 

FIG.  7.    A  drum  of  lenses  used  for  optical  compensation. 

of  moving  spherical  lenses,  since  we  do  not  have  to  worry  about  any 
horizontal  displacement  of  the  lens  element  in  moving  down  across 
the  gate.  The  difficulty  of  using  cylindrical  lenses  is  an  optical  one. 
It  is  necessary  to  assume  that  crossed  cylindrical  components,  one 




FIG.  8.    The  optical  diagram  for  the  system  shown  in  Fig.  7. 

moving,  one  stationary,  can  be  designed  to  behave  like  a  well  corrected 
spherical  lens. 


The  refracting  prism  stationary  in  the  beam  produces  defects  in  the 
image,  giving  errors  of  the  first  type.     The  problem  of  changing  the 



refracting  angle  of  the  prism  in  a  satisfactory  manner  is  difficult  and 
in  some  cases  produces  errors  of  the  second  class. 

If  the  prism  is  used  in  the  beam  on  the  long  optical  side,  as  shown  in 
Fig.  9,  or  even  in  collimated  light,  we  produce  distortion  in  the  image. 
If  the  motion  picture  frame  to  be  projected  is  entirely  above  the 





FIG.  9.    The  distortion  produced  by  a  prism  on  the  long  optical 
side  of  the  projection  lens. 

optical  axis  of  the  lens  and  if  we  use  a  prism  strong  enough  so  that 
the  light  from  the  center  point  of  the  picture  passing  through  at 
minimum  deviation  will  be  deviated  so  as  to  fall  on  the  center  of  the 
screen,  light  from  the  top  of  the  frame  will  pass  through  the  prism  at 
some  angle  differing  from  minimum  deviation  and  will  be  bent  more 

FILM          PRISM         LE:NS 

FIG.  10.    The  astigmatic  effect  caused  by  a  prism  on  the  short  optical 
side  of  the  projection  lens. 

than  it  should  be.  Light  from  the  bottom  of  the  frame  will  also  be 
bent  more  than  it  should  be.  This  will  cause  a  lengthening  of  the 
top  part  of  the  image  and  a  shortening  of  the  bottom  part  of  the 
image.  If  the  prism  is  used  on  the  short  optical  side  of  the  lens,  as 
shown  in  Fig.  10,  light  from  a  point  on  the  film  going  to  various  parts 



[J.  S.  M.  P.  E. 

of  the  lens  will  be  deviated  varying  amounts,  and  the  point  will  be 
imaged  on  the  screen  as  a  line  of  considerable  length. 

Fig.  1 1  shows  the  departure  in  the  angle  of  deviation  from  minimum 
deviation  for  rays  passing  through  prisms  at  various  incident  angles. 
That  these  departures  are  serious  is  shown  from  a  consideration  of  the 
fact  that  a  departure  of  one  minute  in  angle  with  a  2-inch  lens  would 
produce  a  displacement  in  the  center  part  of  the  picture  equivalent  to 
0.001  inch  on  the  film  frame,  if  the  prism  is  assumed  to  be  close  to  the 




10°  PRISM 




-A'        -2* 

+2*       +4°       *6°        +8"      HO* 


FIG.  11.     The  departure  from  minimum  deviation  produced  by  changing 

incident  angle. 

lens  or  on  the  long  optical  side.  If  the  frame  subtends  an  angle  of 
10  degrees  at  the  lens,  a  10-degree  prism  is  necessary  to  shift  the 
image  one-half  frame  on  the  screen.  If  we  consider  the  center  part 
of  the  picture  at  all  times  passing  through  the  prism  at  minimum 
deviation,  rays  from  the  top  of  the  picture  will  be  incident  on  the 
prism,  at  angles  differing  from  the  incident  angle  for  minimum  devia- 
tion by  5  degrees.  This  would  be  serious.  However,  it  may  be 
perfectly  feasible  to  use  a  refracting  prism  on  the  long  optical  side 



if  the  film  frame  subtends  a  small  angle  at  the  lens,  or  on  the  short 
optical  side  if  the  lens  subtends  a  small  angle  at  the  film  frame. 

Fig.  12  shows  a  method  by  means  of  which  we  might  partially 
correct  for  deviation  troubles.  By  using  two  prisms  so  tilted  with 
respect  to  each  other  that  the  ray  which  passes  through  the  first 


12.     A  suggestion  to  eliminate  the  distortion  caused  by  the 
variation  of  deviation  of  a  prism  with  incident  angle. 

prism  at  an  angle  differing  greatest  from  minimum  deviation  goes 
through  the  second  prism  at  minimum  deviation,  and  the  ray  passing 
through  the  first  prism  at  minimum  deviation  passes  through  the 
second  prism  at  an  angle  differing  greatest  from  minimum  deviation, 
the  total  deviation  produced  in  the  two  rays  considered  will  be  prac- 
tically equal. 


FIG.  13.  A 
method  of  con- 
changing  the 
angle  of  devia- 
tion of  a  prism 
to  produce  op- 
tical compen- 


FIG.  14.  A  second  method  of 
continuously  changing  the  angle 
of  deviation  of  a  (compound) 

As  the  film  frame  moves  down  over  the  gate,  it  is  necessary  to 
change  the  refracting  angle  of  the  prism  to  keep  the  center  point  of 
the  image  stationary.  This  changing  of  the  angle  of  the  prism  is  an 
awkward  problem.  Two  methods  are  fairly  feasible.  The  first  is 
shown  in  Fig.  13  and  consists  of  an  annular  disk  which  is  ground  so 

16  F.  TUTTLE  AND  C.  D.  REID  [J.  S.  M.  P.  E. 

that  the  refracting  angle  gradually  changes  from  a  prism  with  its 
thick  side  toward  the  center  of  the  disk  to  a  plane  parallel  plate  and 
then  to  a  prism  with  its  thick  side  toward  the  circumference  of  the 
disk.  The  use  of  this  warped  refracting  element  in  a  projector  intro- 
duces a  skew  distortion  in  the  picture  in  addition  to  the  distortions 
already  discussed  for  the  fixed  prism.  These  new  distortions  become 
small  if  the  prism  disk  is  very  large.  The  use  of  two  warped  refracting 
elements  may  allow  cancellation  of  the  skew  distortion.  Such  an 
element  is  very  difficult  to  make.  Of  course,  it  would  be  very  difficult 
to  achromatize  it.  It  might  be  argued  that  it  is  not  necessary  to 
achromatize  prismatic  elements  which  appear  in  rapid  succession 
first  base  side  up  and  then  base  side  down  in  the  beam  because  per- 
sistence of  vision  would  make  superimposed  complementary  colored 
fringes  appear  nearly  colorless.  The  trouble  with  this  argument, 
however,  is  that  the  limit  of  definition  of  a  horizontal  line  becomes  the 
width  of  the  spectral  image  of  that  line. 

Another  method  of  changing  the  refracting  angle  of  prism  elements 
is  shown  in  Fig.  14.  Two  equal  prisms  placed  with  their  emergent 
and  entrance  faces  together  may  form  a  compound  prism  that  will  act 
as  a  plane  parallel  plate  if  the  thick  side  of  one  is  placed  opposite  the 
thin  side  of  the  other,  as  shown  in  position  A .  Now,  if  these  prisms 
are  each  rotated  through  90  degrees  in  opposite  directions,  we  may 
arrive  to  the  position  B,  which  gives  us  a  compound  prism  of  twice 
the  power  of  its  component  prisms.  It  will  be  noted  that  any  hori- 
zontal displacement  produced  by  one  prism  is  offset  by  an  equal  but 
oppositely  directed  horizontal  displacement  produced  by  its  com- 
panion prism.  The  vertical  refracting  angle,  however,  varies  sinu- 
soidally  from  zero  to  twice  the  refracting  angle  of  the  single  prism. 
When  prisms  of  this  type  are  used  in  a  non-intermittent  projector, 
it  is  necessary  to  reciprocate  them  angularly  with  some  cam  motion 
and  to  have  a  shutter  to  cover  the  return. 


The  mere  presence  of  a  tilting  plane  parallel  plate  used  in  the  beam 
of  light  produces  defects  in  the  image,  while  the  method  of  tilting  it 
also  presents  some  difficulties. 

The  plane  parallel  plate  used  in  a  non-intermittent  projector  will 
have  to  be  used  on  the  short  optical  side  of  the  projector  system,  or 
else  be  tremendously  thick,  since  the  displacement  produced  by  the 
plate  is  a  parallel  one  rather  than  an  angular  one.  On  the  film  side 



of  the  lens  a  parallel  displacement  of  a  fraction  of  an  inch  will  com- 
pensate for  the  full  movement  of  the  film  and  shift  the  screen  image 
several  feet. 

Fig.  15  shows  the  displacement  produced  by  a  plane  parallel  plate, 
and  Fig.  16  shows  the  variation  of  this  displacement  with  the  angle  of 
tilt  of  the  plate  for  a  one-inch  and  a  half -inch  plate.  It  will  be  ob- 




FIG.  15.    The  type  of  displacement  produced  by  a  plane  parallel  plate. 

served  that  the  relation  is  not  a  linear  one,  and  hence  the  proper 
movement  of  the  plates  constitutes  a  problem  unless  the  motion  is  to 
be  controlled  by  a  cam  surface.  The  use  of  a  plane  parallel  plate 
normal  to  the  axis  introduces  spherical  aberration  and  astigmatism. 
Fig.  17  shows  how  a  point  on  the  axis  of  the  lens  is  imaged  as  a  circle 
of  considerable  diameter  on  the  screen.  Fig.  18  shows  the  direction 

FIG.  16.    The  relation  between  the  displacement  produced  by  a  plane 
parallel  plate  and  the  angle  of  tilt  of  the  plate. 

of  rays  from  a  point  off  the  axis  of  the  lens  if  the  rays  pass  through  a 
tilted  plane  parallel  plate  on  the  short  optical  side  of  the  lens.  The 
apparent  definition  on  the  film  is  affected,  then,  by  the  use  of  the 
plate  and  the  position  of  the  plate.  If  a  2-inch  f/2  lens  is  used  with  a 
plate  one-half  inch  thick,  all  of  the  rays  which  reach  the  screen  from 
points  on  the  film  can  be  accounted  for  only  if  we  imagine  the  points 



[J.  S.  M.  P.  E. 

on  the  film  extended  to  a  considerable  size.  The  plane  parallel  plate, 
in  other  words,  is  producing  virtual  images  of  the  points  and  makes 
them  appear  to  the  lens  as  disks  or  streaks.  Fig.  19  shows  the  major 
axis  of  the  confusion  disks  for  different  points  on  the  film  and  for 
different  angular  positions  of  a  one-half  inch  plate.  It  will  be  noted 
that  when  the  plate  is  tilted,  the  position  of  best  apparent  definition  on 
the  film  shifts.  It  is,  of  course,  impossible  to  correct  the  lens  by  any 



FIG.  17.  The  circle  of  confusion  on  the  screen  produced 
by  the  spherical  aberration  of  a  plane  parallel  plate  on  the 
short  optical  side  of  the  projection  lens. 

stationary  means  for  this  varying  astigmatic  effect.  The  use  of  a 
similar  moving  plate  on  the  image  side  of  a  one-to-one  system  might 
seem  at  first  to  offer  a  chance  for  correcting  the  defect,  but  unfor- 
tunately both  spherical  aberration  and  astigmatism  in  such  a  system 
are  additive.  Probably  the  best  the  optical  designer  can  do  is  to 
correct  the  system  for  spherical  aberration  when  the  plate  is  normal. 

FIG.  18.  Blurred  image  on  the  screen  produced  by 
a  tilted  plane  parallel  plate  on  the  short  optical  side  of 
the  projection  lens. 

It  may  be  advantageous  to  use  a  long  focal  length  lens  when  a  tilting 
plate  is  used.  With  a  long  focal  length  lens  the  definition  is  more 
uniform  over  the  area  considered  because  the  film  frame  subtends  a 
much  smaller  angle  at  the  lens.  It  is  not  always  advantageous  to  do 
this,  however.  The  dotted  curve  shown  in  Fig.  19  shows  the  major 
axis  of  confusion  disks  for  a  10-inch  f/2  lens  when  a  one-half  inch 
plate  is  tilted  at  10  degrees.  Comparison  of  the  definition  obtained 



in  this  manner  with  that  obtained  with  a  one-half  inch  plate  tilted  at 
10  degrees  with  the  2-inch  f/2  lens  shows  that  we  do  not  gain  in  defini- 
tion until  we  get  some  distance  below  the  axis  or  considerably  above 
the  axis. 

The  size  of  the  astigmatic  image  is  very  materially  reduced  if  the 
aperture  of  the  lens  is  limited  in  the  vertical  dimension.  We  have  to 
consider  only  a  small  pencil  of  rays  passing  through  the  plate.  There 


2  .3  A  5  .6 



FIG.  19.  The  magnitude  of  the  major  axis  of  confusion  disk  caused  by  a  one- 
half  inch  plane  parallel  glass  plate  in  conjunction  with  a  2  inch//2  projection 
lens  as  a  function  of  the  distance  of  the  object  point  off  the  axis  for  different 
tilts  of  the  plate.  The  dotted  curve  refers  to  a  10  inch//2  lens  with  the  plate 
tilted  at  10  degrees. 

are  two  unfortunate  things  about  limiting  this  vertical  angle,  however: 
one,  considerable  light  is  lost  and,  two,  it  does  not  rid  us  of  the  distor- 
tion effect  which  is  present  with  a  tilted  plate.  Fig.  20  shows  dia- 
grammatically  how  this  distortion  is  produced. 

Under  certain  conditions  the  distortion  effect  may  be  improved 
by  using  two  plates,  each  of  half  the  original  single -plate  thickness, 
placed  one  on  each  side  of  a  one-to-one  optical  system,  as  in  Fig.  21. 



[J.  S.  M.  P.  E. 

When  the  plates  are  normal  to  the  optic  axis  there  is  no  distortion. 
When  the  plates  are  tilted,  the  distortion  is  somewhat  corrected. 

If  we  are  willing  to  use  a  cam  to  oscillate  the  plate  and  a  long  focal 
length  lens  with  a  restricted  vertical  aperture,  we  can  have  theoreti- 
cally good  projection  with  a  single  plate  tilting  in  the  beam.  The 



FIG.  20.     Distortion  produced  by  a  plane  parallel  plate 
on  the  short  optical  side  of  the  projection  lens. 

screen  picture,  however,  would  be  small  unless  we  relay  the  image. 
The  loss  of  light  in  such  a  system,  especially  with  the  relay  and  with  a 
shutter  which  would  cover  the  return  of  the  plate  and  have  flicker 
blades,  would  rule  out  such  a  projector. 





FIG.  21.  The  partial  correction  of  the  distortion 
produced  by  a  plane  parallel  plate  by  the  use  of  two 
similar  plates  on  opposite  sides  of  a  lens  working  at 
unit  magnification. 

If  we  want  to  follow  the  film  with  uniformly  rotating  plates,  we  find 
in  Fig.  22  that  we  will  have  to  use  a  plate  3  inches  thick,  even  for 
following  16-mm.  film  over  the  displacement  of  plus  or  minus  half  a 
frame,  if  we  are  to  stay  within  our  steadiness  tolerance  of  0.0005 
inch.  We  can  rotate  this  plate  through  an  angle  of  only  8  degrees  and 



since  we  will  have  to  have  another  plate  ready  to  follow  the  next 
frame,  we  will  have  to  have  48  plates  arranged  on  a  drum.  Such  a 
projector  would  be  quite  impracticable. 

A  very  ingenious  use  of  parallel  plates  can  be  found  in  one  pro- 
jector. By  arranging  plates  as  shown  in  Fig.  23  with  the  plates 
making  an  angle  with  their  axis  of  rotation,  but  normal  to  the  optical 
axis  in  their  mid-position,  it  is  possible  to  have  the  vertical  com- 


9        10 

t    IN  INCHES 

FIG.  22.  The  departure  from  a  linear  relation  between  the  displacement 
produced  by  a  plane  parallel  plate  and  the  angle  of  tilt  with  respect  to  plate 
thickness,  for  various  total  displacements. 

ponent  of  the  displacement  produced  very  nearly  linear  with  the 
angle  of  rotation.  The  undesired  horizontal  component  of  the  dis- 
placement can  be  compensated  for  by  having  other  plates  rotating 
in  the  same  manner  some  place  in  the  system  in  such  a  way  that  the 
vertical  displacements  are  additive  and  the  horizontal  displacements 
offset  one  another.  With  this  arrangement  it  is  still  necessary,  how- 
ever, to  restrict  the  vertical  angles  subtended  by  the  lens  to  get  rid 
of  astigmatism. 



[J.  S.  M.  P.  E. 

Plane  reflecting  surfaces  can  be  used  in  the  beam  without  producing 
any  defects  in  the  image.  The  single  tilting  mirror,  however,  can  not 
be  used  alone  without  distorting  the  image.  The  method  used  for 
moving  reflecting  elements  also  introduces  errors  in  the  image. 

In  Fig.  24  there  is  shown  a  reflecting  mirror  tilted  in  the  long 





FIG.  23.  A  special  method  of  tilting  plane  parallel 
plates  to  produce  a  good  approximation  to  a  linear  rela- 
tion between  the  vertical  component  of  the  displacement 
and  the  angular  displacement  about  the  axis  of  rotation  of 
the  plates. 

optical  side  of  a  projection  system.  When  the  mirror  is  at  45  degrees 
the  plane  of  the  image  formed  by  the  system  makes  an  angle  of  90 
degrees  with  the  plane  of  the  film  gate.  If  the  mirror  is  tilted  through 
an  angle  sufficient  to  place  the  center  of  the  frame,  which  is  entirely 
above  the  axis  of  the  lens  on  the  center  of  the  screen,  the  plane  of  the 
image  does  not  correspond  with  the  plane  of  the  screen  but  falls  along 



the  dotted  line  shown  in  Fig.  24.  The  image  is  rectilinear  in  its 
plane  but,  of  course,  is  not  projected  on  to  the  screen  plane  as  a 
rectilinear  image,  nor  is  it  exactly  in  focus.  Because  the  image  plane 
does  not  correspond  to  the  screen  plane,  the  screen  image  is  dis- 
torted in  two  directions.  Vertical  lines  on  the  film  will  not  be  parallel, 
the  top  edge  of  the  picture  being  either  narrower  or  wider  than  the 
bottom  edge  of  the  picture/  Horizontal  lines  on  the  picture  will  be 
imaged  as  parallel  lines  on  the  screen,  but  horizontal  lines  equally 
spaced  on  the  film  will  not  be  equally  spaced  on  the  screen.  If  the 
angle  through  which  the  mirror  has  to  be  tilted  to  keep  the  center  of 

PLANE:  or  rocus 





FIG.  24.     Optical  compensation  for  the  film  motion 
produced  by  a  tilting  mirror  in  the  light  path. 

the  frame  imaged  on  the  center  of  the  screen  is  small,  this  keystoning 
distortion  will  not  be  serious.  Hence,  with  a  long  focal  length  lens 
we  will  be  able  to  tilt  the  mirror  by  some  cam  mechanism  and  have  a 
satisfactory  picture  on  the  screen.  If  we  want  to  avoid  the  use  of 
cams  and  change  the  angle  of  tilt  of  the  mirror  linearly  with  time, 
we  can  mount  a  series  of  mirrors  on  the  periphery  of  a  drum  and  rotate 
the  drum  with  uniform  angular  velocity.  This  sort  of  system  of 
moving  the  mirrors,  however,  will  affect  the  steadiness  of  the  center 
point  of  the  picture  on  the  screen.  If  we  use  a  straight  gate  and  the 
film  is  moving  at  a  constant  linear  speed  through  this  gate,  it  is  the 



[J.  S.  M.  P.  E. 

tangent  of  the  angle  which  the  center  of  the  frame  subtends  at  the 
lens  from  the  axis  of  the  lens,  which  is  going  to  vary  linearly  with 
time  and  not  the  angle  itself.  Mr.  H.  Dennis  Taylor  in  a  paper 
published  in  The  Photographic  Journal,  February,  1924,  has  shown 
that  to  get  satisfactory  projection  with  a  system  using  a  uniformly 
rotating  drum  of  mirrors  with  35-mm.  film,  it  is  necessary  to  use  about 
60  mirrors  in  the  drum.  The  possible  ways  that  have  been  proposed 
for  reducing  the  defects  produced  in  the  image  by  a  tilting  mirror 
have  involved  the  use  of  curved  gates  and  toroidal  lenses.  We  feel 


FIG.  25.    A  method  of  following  moving  film  by 
the  motion  of  a  prism  reflector. 

certain  that  a  curved  gate  could  be  used  to  correct  to  some  extent  for 
the  distortion  in  the  image.  A  very  satisfactory  projector  has  been 
designed  which  uses  a  series  of  cam  actuated  mirrors  and  a  curved 
gate.  A  discussion  of  nonrectilinear  lenses  is  beyond  the  scope  of  this 

Fig.  25  shows  how  two  reflecting  surfaces  can  be  moved  together 
and  keep  the  image  from  moving  film  stationary  on  the  screen.  In 
this  figure  the  reflecting  surfaces  are  two  faces  of  a  right  angle  prism. 
It  is  evident  that  the  mechanical  problem  of  moving  a  series  of  prisms 
of  this  form  at  a  constant  linear  speed  and  in  a  straight  path  in  front  of 



the  gate  is  difficult.  The  correcting  element  occupies  considerable 
space,  and  it  is  difficult  to  have  a  second  element  ready  to  follow  a 
second  frame  past  the  gate  as  soon  as  the  first  frame  reaches  the 
bottom  of  the  gate.  Further,  the  size  of  the  prism  is  considerable 
and  the  back  focus  of  the  projection  lens  has  to  be  long. 

In  Fig.  26  we  have  shown  how  reflecting  surfaces  of  rhomb  prisms 
may  be  moved  to  give  a  vertical  optical  displacement  of  the  image. 
A  single  rhomb  gives  a  parallel  displacement  to  light  which  is  equal  to 
the  face  of  the  rhomb.  If  the  rhomb  is  held  in  one  position  in  the 
projection  system,  this  displacement  is  all  a  vertical  displacement. 

FIG.  26.     The  use  of  pairs  of  reflecting  rhombs  to 
produce  a  stationary  image  from  moving  film. 

If  the  rhomb  is  rotated  through  90  degrees,  the  vertical  displacement 
is  zero,  the. whole  displacement  being  horizontal.  Horizontal  dis- 
placements of  course  are  not  desired  in  a  non-intermittent  projector. 
The  figure  shows  how  two  rhombs  may  be  rotated  together  in  such  a 
manner  that  the  horizontal  displacement  of  the  image  is  zero  and 
still  allow  a  vertical  displacement.  If  the  wheels  carrying  the  rhombs 
are  rotated  with  uniform  angular  velocity,  the  displacement  effected 
by  the  system  varies  not  linearly  but  sinusoidally  with  time.  Here 
again,  then,  we  see  that  we  will  have  to  use  a  large  number  of  rhombs 
to  get  satisfactory  projection.  We  would  like  to  point  out  that  the 



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5  S.  § 

28  F.  TUTTLE  AND  C.  D.  REID  [J.  S.  M.  P.  E. 

path  between  the  film  and  the  lens  is  very  long  and  we  will  have  to 
use  a  long  back  focus  lens  for  projecting  with  this  system. 


A  number  of  inventors  have  proposed  the  use  of  spiral  image-form- 
ing refracting  or  reflecting  elements.  These  elements,  of  course, 
would  be  very  difficult  to  make.  Their  only  advantage  would  likely 
be  in  the  fact  that  they  would  simplify  the  problems  of  moving  the 
optical  part  in  the  beam.  Their  use  would  probably  introduce  a 
twisting  distortion  in  the  image. 


We  know  that  the  four  types  of  elements — lenses,  prisms,  plates, 
and  mirrors — can  be  used  under  proper  conditions  to  produce  satis- 
factory pictures  as  far  as  quality  is  concerned.  The  projected  picture 
is  steady  enough,  free  enough  from  distortion,  and  the  definition  is 
passable.  It  is  possible  to  have  the  number  of  glass-air  surfaces  small 
enough  so  that  the  picture  is  not  made  flat  because  of  flare.  In  some 
cases  we  have  found  that  the  focal  length  of  the  lens  has  to  be  longer 
than  desirable,  and  we  might  have  to  use  a  relay  system  for  getting 
the  image  large  enough  on  the  screen.  These  relay  systems  would 
introduce  additional  surfaces  which  certainly  may  lose  a  considerable 
amount  of  light.  In  some  cases  we  found  that  to  get  a  satisfactory 
picture  we  had  to  limit  the  /  aperture  of  the  projection  lens.  This, 
of  course,  will  cut  down  on  light.  We  have  not  discussed  very  fully 
the  problem  of  keeping  the  light  constant  to  the  screen  during  the 
period  which  we  use  to  change  over  from  projecting  from  one  frame 
to  projecting  from  the  successive  frame.  Any  method  we  use,  how- 
ever, is  very  likely  to  limit  the  light  to  some  part  of  the  picture  during 
the  change-over  period.  With  moving  lenses  there  will  be  some 
barrel  cutting  and  some  loss  of  light  from  points  which  are  consider- 
ably off  the  axis  of  the  lens.  With  prisms  we  can  not  change  suddenly 
from  a  prism  base  side  up  to  a  prism  base  side  down  without  cover- 
ing up  the  period  of  that  change.  Plane  parallel  plates  joined  to- 
gether so  as  to  pass  successively  in  front  of  the  gate  will  have  a  divid- 
ing line  between  plates,  which  appears  to  the  film,  because  of  refrac- 
tion, to  have  considerable  width.  Even  mirrors  can  hardly  be 
joined  together  so  that  the  dividing  line  between  them  is  fine  enough 
not  to  affect  the  light  to  the  screen.  Any  change  in  the  amount  of 
light  to  the  screen  during  the  projection  period  demands  the  use  of  a 
shutter  and  flicker^blades  or  some  fixed  diaphragm  which  will  keep 

Jan.,  1933]          CONTINUOUSLY  MOVING  FlLM  PROJECTION  29 

the  light  constant.  Either  method  will  lose  light  to  the  screen. 
Many  of  the  systems  require  a  moving  condenser  system  to  get  even 

The  precision  requirements  on  the  mechanical  parts  used  in  a  non- 
intermittent  projector  can  be  computed  by  finding  the  angle  or  dis- 
tance through  which  we  can  move  the  optical  elements  with  the  film 
stationary  without  shifting  the  image  on  the  screen  in  an  objectionable 
amount.  The  pitch  of  the  sprocket  must  be  equal  to  the  pitch  of  the 
film  to  within  0.0005  inch  in  one  perforation  pitch  if  we  are  going  to 
project  the  picture  continuously  and  keep  that  picture  steady  on  the 
screen.  It  may  be  necessary  to  have  the  optical  elements  used 
precisely  matched,  and  the  initial  adjustment  of  the  elements  pre- 
cisely made.  These  precision  requirements,  of  course,  will  add  to  the 
cost  of  producing  the  projector. 

If  we  are  going  to  gain  in  quietness  of  the  projector,  we  can  not 
rapidly  reciprocate  parts  which  have  considerable  mass  or  moments  of 
inertia.  We  can  gain  in  quietness,  however,  if  the  projector  design 
allows  us  to  move  all  parts  with  constant  angular  velocity  and  have 
all  parts  counterbalanced.  Many  of  the  systems  proposed  impose 
special  limitations  on  the  projector.  For  some  of  them  to  work  satis- 
factorily they  would  have  to  have  ridiculous  physical  dimensions. 
vSome  of  them  demand  a  fixed  screen  distance  or  a  variable  focal 
length  auxiliary  projection  lens.  Some  of  them  demand  a  special 
arrangement  of  pictures  on  the  film.  Several  do  not  provide  any 
framing  for  the  picture  except  at  the  screen.  Very  few  of  them 
could  be  considered  as  projectors  for  projecting  lenticulated  color 


JENKINS,  C.  F.:  "Continuous  Motion  Picture  Machines,"  Trans.  Soc.  Mot. 
Pict.  Eng.  (May,  1920),  No.  10,  p.  97. 

JENKINS,  C.  F.:  "Continuous  Motion  Projector  for  the  Taking  of  Pictures 
at  High  Speed,"  Trans.  Soc.  Mot.  Pict.  Eng.  (May,  1921),  No.  12,  p.  126 

JENKINS,  C.  F.:  "Prismatic  Rings,"  Trans.  Soc.  Mot.  Pict.  Eng.  (May,  1922), 
No.  14,  p.  65. 

STEWART,  FRANK  N.:  "Note  on  New  Continuous  Projector,"  Trans.  Soc. 
Mot.  Pict.  Eng.  (May,  1922),  No.  14,  p.  162. 

FORCH,  C.:  "Der  optische  Ausgleich  der  Bildwanderung  in  der  Kinemato- 
graphie,"  Zeit.  Wiss.  Phot.  (1921-22),  No.  21,  p.  201. 

BENNET,  C.  N.:  "Continuous  Motion  Projectors,"  Kinemat.  Weekly  (Jan. 
11,  1923),  No.  71,  iv. 

TAYLOR,  H.  D.:  "The  Feasibility  of  Cinema  Projection  from  a  Continuously 
Moving  Film,"  Trans.  Opt.  Soc.  (1923-24),  No.  25,  p.  149. 

30  F.  TUTTLE  AND  C.  D.  REID 

WEISS,  K.:  "Die  Ringlinse  als  optischer  Ausgleich  der  Filmbildwanderung," 
Phot.  Ind.  (Aug.  22,  1923),  p.  419. 

BOWEN,  LESTER,  AND  GRIFFIN,  HERBERT:  "Is  the  Continuous  Projector 
Commercially  Practical?"  Trans.  Soc.  Mot.  Pict.  Eng.  (May,  1924),  No.  18,  p.  147. 

RUHNAU,  R.:  "Projektoren  mit  optischem  Ausgleich,"  Kinotechnik  (Oct.  20, 
1927),  No.  9,  p.  529. 

LEVENTHAL,  J.  F.:  "Projectors  with  Optical  Intermittents,"  Trans.  Soc. 
Mot.  Pict.  Eng.,  XII  (Apr.,  1928),  No.  34,  p.  406. 

LEVENTHAL,  J.  F.:  "A  New  Optical  Compensator,"  Trans.  Soc.  Mot.  Pict. 
Eng.,  XII  (Sept.,  1928),  No.  36,  p.  1068. 

HOLMAN,  A.  J.:  "A  Non-Intermittent  Optical  Projector,"  Trans.  Soc.  Mot. 
Pict.  Eng.,  XII  (Sept.,  1928),  No.  36,  p.  1184. 

"The  Mechau  Projector,"  Trans.  Soc.  Mot.  Pict.  Eng.,  XII  (Sept..  1928),  No. 
36,  p.  1193. 

HATSCHEK,  P.:  "Optical  Compensation  in  Photography  and  Projection," 
Kinotechnik  (July,  1929),  No.  11,  p.  367. 

HOLMAN,  A.  J.:  "Apparatus  Developed  to  Simplify  Manufacture  of  Lens 
Wheels  for  Continuous  Projectors,"  /.  Soc.  Mot.  Pict.  Eng.,  XIV  (June,  1930), 
No.  6,  p.  623. 

CoNTiNSOUZA-CoMBEs:  "Note  sur  la  Projection  a  Deroulement  Continu  et 
1'appareil  Continsouza-Combes,"  Butt.  Soc.  Franc.  Phot.  (May,  1928),  No.  15, 
p.  119. 






Summary. — This  paper  presents  a  brief  description  of  the  advantages  of  optical 
compression  for  producing  wide  screen  pictures.  There  is  included  an  exposition 
of  the  design  and  operating  characteristics  of  cylindrical  compression  objectives, 
with  particular  reference  to  the  high  degree  of  central  and  marginal  definition  at- 
tainable. This  latter  is  compared  with  the  performance  of  existing  motion  picture 
lenses.  In  this  connection  there  is  presented  a  detailed  quantitative  description  of 
the  definition  attainable  with  high-grade  motion  picture  lenses.  These  data  are 
correlated  with  information  as  to  the  physiological  requirements  for  satisfactory 
definition  on  the  screen. 


All  lenses  of  whatever  nature  fall  short  of  producing  perfectly 
sharp  images.  Satisfactory  motion  pictures  are  possible  because 
in  the  conditions  under  which  the  pictures  are  observed  the  eye  does 
not  readily  detect  imperfections  that  are  below  a  certain  level. 
The  choice  of  any  method  of  producing  wide  screen  pictures  will 
depend  to  a  considerable  extent  on  the  possibility  of  obtaining 
images  of  suitable  quality.  If  a  method  that  produces  suitable 
images  be  also  economical  and  easy  to  apply,  the  combination  is 
ideal.  If  the  method  be  neither  economical  nor  optically  satis- 
factory, it  has  little  to  recommend  it. 

In  order  to  form  an  intelligent  opinion  about  the  relative  merits  of 
different  methods  of  producing  wide  screen  pictures,  one  must  have 
certain  precise  information  about  the  definition  that  is  obtained  with 
motion  picture  lenses  on  standard  film  and  how  this  definition  is 
influenced;  in  the  one  case  by  optical  compression  with  cylindrical 
lenses,  and  in  the  other  case  by  increasing  the  width  of  the  film  and 

*  Presented  at  the  meeting  of  a  New  York  Section,  June  8,  1932. 
*  *  Consulting  engineer,  New  York,  N.  Y. 


32  H.  S.  NEWCOMER  [j.  s.  M.  P.  E. 

the  area  to  be  sharply  covered  by  the  lens.  It  is  from  this  point  of 
view  that  the  subject  is  here  presented. 

This  paper  presents  a  brief  description  of  the  design  and  operating 
characteristics  of  cylindrical  compression  objectives  together  with  an 
account  of  their  advantages  and  performance  possibilities  when  used 
to  produce  wide  screen  pictures  on  standard  motion  picture  film. 
The  subject  is  presented  both  from  the  point  of  view  of  the  perform- 
ance of  existing  lenses  and  of  the  mathematical  and  physiological 
considerations  fixing  the  optimum  quality  of  projected  images.  It  is 
shown  that  all  the  better  motion  picture  lenses  approach  a  quality 
that  is  little  more  than  sufficient  to  meet  modern  theater  require- 

The  central  portions  of  the  picture  are  naturally  subjected  to  the 
closest  scrutiny,  and  there  the  best  definition  attainable  is  almost 
twice  what  the  critical  observer  requires.  On  the  other  hand,  the 
peripheral  portions  of  the  image  are  much  worse,  being  subjected  to  a 
number  of  deteriorating  influences  that  appreciably  increase  as  the 
border  of  the  present  image  frame  is  reached  and  passed. 


Thus,  from  an  optical  point  of  view,  standard  film  has  many  ad- 
vantages, and  the  importance  of  the  dimensions  of  the  frame  in 
forming  suitably  sharp  images  becomes  apparent  only  after  one 
has  had  an  opportunity  to  study  the  performance  characteristics 
of  motion  picture  lenses.  This  not  only  has  an  important  bearing 
on  the  dimensional  relations  obtaining  in  present-day  practice, 
but  it  very  seriously  handicaps  the  use  of  wide  film  and  affords  a 
considerable  advantage  to  optical  compression  as  a  means  of  obtain- 
ing laterally  extended  screen  images. 

Thus,  from  the  point  of  view  of  sharpness  of  image,  the  results 
attained  by  the  compression  or  anamorphosing  objective  are  superior 
to  those  afforded  by  wide  film.  This  advantage  is  by  no  means  the 
sole  merit  of  the  method.  The  anamorphoser  comes  into  play  only 
twice  in  the  entire  sequence  of  operations  from  the  taking  of  the 
picture  to  its  projection  on  the  screen;  namely,  at  the  beginning, 
when  it  is  placed  in  front  of  the  ordinary  camera  equipment  used  to 
take  the  picture,  and  at  the  end,  when  it  is  placed  in  front  of  the 
projector  to  expand  the  picture  on  the  screen.  In  all  the  many 
stages  of  processing  and  handling,  the  film  is  treated  as  ordinary 
standard  film,  and  the  tremendous  expense  involved  in  providing 

Jan.,  1933]  WlDE  SCREEN  PHOTOGRAPHY  33 

special  equipment  for  processing,  packaging,  and  projecting  wide 
film  is  all  avoided.  The  anamorphoser  permits  wide  screen  pictures 
of  excellent  quality  to  be  shown  interchangeably  with  standard  pic- 
tures, and  the  method  may  be  used  for  either  whole  features  or  par- 
ticular scenes  as  desired.  Contrary  to  current  opinion  it  is  extremely 
easy  to  mount  cylindrical  compression  systems  on  both  cameras  and 


In  taking  the  picture,  the  effect  of  the  anamorphoser  is  to  com- 
press a  wide  picture  into  a  relatively  narrow  space.  The  compres- 
sion is  produced  by  a  device  that  acts  like  an  inverted  telescope, 
but  in  one  meridian  only.  The  cylindrical  anamorphoser  is  com- 
posed, in  its  simplest  form,  of  a  positive  and  a  negative  cylindrical 
member  with  axes  parallel  and  arranged  in  the  manner  of  an  ordinary 
opera  glass  or  Galilean  telescope.  The  anamorphoser  is  afocal; 
hence  its  interposition  in  front  of  the  ordinary  camera  or  projection 
lens  does  not  alter  the  focus  of  the  lens.  During  the  photographing, 
the  anamorphoser  merely  compresses  the  image  of  the  laterally  ex- 
tended scene  into  a  narrow  film  space;  during  projection  it  expands 
the  projected  film  image  to  an  increased  width  on  the  screen. 

The  cylindrical  anamorphoser  is  not  a  recent  development,  even 
in  motion  picture  work.  Ernest  Abbe  many  years  ago  described  all 
the  types  used  today.  At  the  beginning  of  the  present  motion  pic- 
ture era,  Zollinger  proposed  to  use  them  to  compress  the  image  and 
save  expenditure  for  film.  It  was  only  recently,  however,  that 
serious  attempts  were  made  to  rid  these  anamorphosers  of  the  con- 
siderable color  and  other  imagery  defects  which  they  exhibited  and  to 
correct  them  to  the  degree  required  in  motion  picture  work.  Many 
attempts  at  improving  the  photographic  quality  of  these  systems 
have  not  been  very  successful.  Only  a  short  time  ago  Mr.  H.  W.  Lee, 
in  speaking  before  the  Royal  Photographic  Society,  called  attention 
to  the  fact  that  "the  designing  of  these  systems  was  exceedingly 
laborious,  and  the  manufacture  of  deforming  systems  with  cylindrical 
lenses  far  more  difficult  than  of  optical  systems  with  spherical  sur- 

However,  as  is  often  the  case,  once  a  satisfactory  solution  has 
been  obtained,  the  problem  appears  much  simpler.  As  a  matter  of 
fact,  if  certain  features  of  design  be  adhered  to,  features  that  involve 
among  other  things  the  relative  indices  of  the  glasses  used  and  the 
orientation  of  the  cemented  surfaces  and  the  cambrures  of  the  ele- 



[J.  S.  M.  P.  E. 

ments,  an  extremely  simple  system  that  is  unusually  free  from  aberra- 
tions of  every  sort  can  be  designed.  Figs.  1  and  2  show,  respectively, 
a  photograph  and  a  cross-section  of  a  fully  corrected  anamorphoser, 
and  serve  to  illustrate  its  simple  and  compact  construction.  This 
anamorphoser  is  used  without  any  supplementary  correcting  system, 
none  being  necessary. 

FIG.  1.  Cylindrical  anamorphoser:  left,  mounted  in  front  of  a  1-inch 
lens  in  company  with  a  2-inch  and  4-inch  lens  on  the  same  turret;  right, 
on  a  bracket  suspending  it  in  front  of  any  of  three  lenses  on  turret. 

The  aberrations  of  cylindrical  systems  of  this  sort  are,  in  a  way, 
analogous  to  those  of  spherical  systems.  In  correcting  for  the 
imagery  at  the  central  portion  of  the  field,  once  axial  astigmatism  is 
obviated  by  proper  spacing  arrangements,  it  remains  only  to  rid  the 
system  of  spherical  and  chromatic  aberrations.  This  may  be  done 
by  correcting  each  individual  member  separately.  The  residual 

FIG.  2.     A  cross-section  of  a  fully  corrected  anamorphoser. 

secondary  spectrum,  and  the  zonal  errors  are  then  of  similar  magni- 
tude and  opposite  sign,  so  that  the  assembled  system  may  be  ex- 
ceptionally well  corrected  for  axial  image  points.  In  fact,  the  writer 
has  found  that  by  thus  largely  ridding  each  member  separately  of 
spherical  aberration,  the  zonal  spherical  aberrations  of  the  system 
as  a  whole  may  indeed  be  made  so  small  as  to  have  a  maximum  value 

Jan.,  1933] 



of  one  part  in  thirty  thousand,  equivalent  to  a  longitudinal  focusing 
error  of  one  part  in  one  hundred  and  eighty  thousand  for  an  as- 
sociated 50-mm.  camera  lens.  The  paraxial  color  focal  difference  in 
the  spectral  interval  C  to  F  may  be  one  part  in  seven  thousand  and 
the  zonal  color  differences  one  part  in  ten  thousand,  corresponding, 
respectively,  to  one  part  in  forty  thousand  and  one  part  in  sixty 
thousand  for  the  associated  50-mm.  lens.  These  are,  of  course, 
fantastically  and  unnecessarily  small  errors. 


This  leads  us  to  a  consideration  of  the  color  correction  for  marginal 
or  extra-axial  points  of  the  image.  The  writer  has  found  it  possible 
by  suitably  constructing  the  two  members,  to  eliminate  astigmatism 
and  coma  along  inclined  rays;  in  other  words,  to  make  all  the  rays 
of  any  entering  bundle  of  parallel  rays  traverse  the  objective  and 
emerge  from  it  still  parallel.  (See  Fig.  2,  and  Fig.  3  at  C.)  This 





FIG.  3.  Curves  showing,  for  a  certain  anamorphoser, 
the  angular  spread  of  the  three  rays  shown  at  the  right  in 
Fig.  2  when  the  rays  at  the  left  are  parallel  and  at  an 
angle  of  7.05  degrees  to  the  axis.  Ordinates  are  angles 
with  the  axis. 

parallelism  can  be  made  practically  absolute  for  all  the  rays  of  a  par- 
ticular bundle,  provided  the  light  is  monochromatic.  But  if  the 
objective  be  composed,  as  just  described,  of  members  individually 
fully  achromatized  in  the  usual  manner  so  as  to  be,  as  far  as  possible, 
free  of  color  focal  differences  along  the  axis,  there  remains  an  ap- 
preciable lack  of  parallelism  of  the  different  colored  rays  of  an  in- 



[J.  S.  M.  P.  E. 

clined  bundle,  and  hence  a  color  fringe  in  the  marginal  areas  of  the 
picture.  Fig.  3  illustrates  the  extent  of  such  an  error  for  a  beam  of 
parallel  rays  inclined  7  degrees  on  the  camera  side.  The  abscissas 
of  Fig.  3  are  wavelengths,  designated  by  the  conventional  letters, 
and  the  ordinates  are  the  angles  of  emergence  with  respect  to  the 
axis.  Only  the  emergence  angles  for  the  central  and  two  outside 

C  d  e  r  q  h 

FIG.  4.  Same  as  Fig.  3,  but  referring  to  an  ana- 
morphoser  specially  corrected  to  improve  or  narrow  the 
color  dispersion  in  the  region  e  to  h. 

rays  of  such  a  beam  are  plotted.  (See  also  Fig.  2.)  The  maximum 
entrance  height  on  the  positive  member  as  plotted  is  1/20  the  focal 
length  of  the  member.  This  corresponds  to  a  15-mm.  half -opening 
on  the  objective  used  in  the  demonstration,  half  its  maximum  open- 


FIG.  5.  Same  as  Fig.  3,  but  referring  to  an  anamor- 
phoser  specially  corrected  to  improve  or  narrow  the  color 
dispersion  in  the  region  C  to  g,  where  visibility  and  Mazda 
lighting  are  most  effective. 

ing.     Fig.  2  shows  the  position  of  such  a  ray  with  respect  to  an  as- 
sociated/72.3  50-mm.  camera  lens. 

The  curves  of  Fig.  3  show  an  angular  emergence  difference  for  the 
spectral  interval  C  to  h  of  0.06  degree,  corresponding  to  a  diffusion 
circle  of  0.035  millimeter  for  an  associated  50-mm.  camera  lens,  the 
angle  being  two- thirds  as  large  on  that  side.  At  an  inclination  of 

Jan.,  1933]  WlDE  SCREEN  PHOTOGRAPHY  37 

10.5  degrees,  that  is,  for  a  point  near  the  margin  of  the  picture,  the 
difference  is  greater,  and  the  diffusion  circle  is  about  0.06  millimeter 
in  diameter.  Although  the  actual  effective  error  is  somewhat  less 
than  this,  nevertheless  it  is  added  to  the  relatively  poor  marginal 
performance  of  the  camera  and  projection  lenses,  and  therefore  must 
be  reduced. 

There  is  an  unusual  and  interesting  method  of  eliminating  this 
large  marginal  color  error,  namely,  by  only  partially  achromatizing 
each  of  the  two  members  of  the  anamorphoser.  Fig.  4  gives  the 
curves  for  a  10. 5 -degree  angle  for  an  anamorphoser  thus  corrected, 
in  this  instance  in  such  fashion  as  to  reduce  the  angular  difference, 
F  to  h,  to  about  0.01  degree  at  a  fractionally  smaller  opening.  The 
operating  characteristics  of  this  anamorphoser  are  obviously  excellent 
when  used  for  photography  in  daylight  with  either  ordinary  or  pan- 
chromatic stock.  The  marginal  diffusion  circle  of  the  50-mm. 
camera  lens  caused  by  the  anamorphoser  is  only  0.006  millimeter. 

Fig.  5  represents  a  slightly  lesser  degree  of  primary  underachromati- 
zation,  the  purpose  of  which  is  to  bring  the  maximum  marginal 
correction  into  the  spectral  region  C  to  g.  This  anamorphoser  gives 
optimum  results,  either  for  projection  or  for  studio  photography. 
In  projection,  although  the  absolute  aperture  is  larger,  the  angle  is 
less,  so  that  the  curves  are  not  much  different. 

For  convenience  in  interpreting  the  significance  of  the  color 
corrections,  there  is  drawn  on  Fig.  3  a  sensitivity  curve  of  Eastman 
panchromatic  emulsion.  The  curve  is  drawn  to  an  arithmetical 
scale,  and  not  a  logarithmic  scale  as  is  usually  the  case.  The  ordi- 
nates  are  estimated  from  readings  of  wedge  spectra,  the  curve  being 
then  corrected  by  integrating  various  color  regions  and  adjusting 
the  curve  so  that  the  integrals  correspond  to  the  respective  published 
exposure  times. 

In  Fig.  5  are  plotted  a  visibility  curve  and  a  sensitivity  curve  for 
Mazda  illumination.  The  sensitivity  curve  is  derived  from  the 
curve  of  Fig.  3  by  multiplying  the  ordinates  of  Fig.  3  by  the  corre- 
sponding ordinates  of  a  tungsten  filament  emission  curve  and  dividing 
by  those  for  daylight  energy  distribution.  The  abscissas  of  Figs. 
3,  4,  and  5,  representing  wavelengths,  are  drawn  to  logarithmic  scale. 


Despite  the  existence  of  only  a  partial  achromatization  along  the 
axis  of  each  of  the  two  members,  the  objective  as  a  whole  yet  has  a 

38  H.  S.  NEWCOMER  [J.  S.  M.  P.  E. 

very  satisfactory  paraxial  and  spherical  color  correction,  one  part  in 
seven  hundred  and  one  in  a  thousand,  respectively.  The  resulting 
diffusion  circles  for  an  associated  50-mm.  camera  lens  are  less  than 
0.002  millimeter  in  diameter,  a  value  that,  as  will  be  seen,  is  too 
small  to  produce  any  deteriorating  effect  on  the  quality  of  a  motion 
picture  image.  These  figures  (increased  by  50  per  cent  for  good 
measure)  for  the  diffusion  circles  at  the  center  and  margin  of  standard 
film  due  to  the  anamorphoser  are  plotted  in  Fig.  7,  where  they  may 
be  compared  with  the  much  greater  diffusion  of  the  image  resulting 
from  the  defects  of  the  camera  lens  itself. 

Since  the  anamorphoser  is  afocal,  its  relative  opening  depends  only 
on  its  absolute  size.  It  is,  in  fact,  convenient  to  choose  the  size  so  as 
to  reduce  the  aberrations  considerably  below  those  of  the  spherical 
objective  with  which  the  anamorphoser  is  associated.  The  anamor- 
phoser has,  therefore,  an  almost  negligible  deteriorating  effect  upon 
the  image.  In  fact,  the  very  slight  effect  observed  must  be  attributed 
almost  entirely  to  the  interposition  of  the  four  air-to-glass  refracting 
surfaces.  It  amounts  at  the  most  to  a  difference  of  one  stop;  and 
since  motion  picture  lenses  are  now  available  that  are  appreciably 
more  than  this  amount  superior  to  most  motion  picture  lenses  now 
in  common  use,  it  will  be  obvious  that  one  can  obtain  all  the  ad- 
vantages of  the  anamorphoser  for  the  production  of  wide  screen 
pictures  and  yet  retain  the  quality  of  picture  to  which  the  critical 
observer  is  now  accustomed. 

Except  for  the  slight  effect  of  surface  loss,  the  anamorphoser  does 
not  increase  the  required  exposure  time.  On  projection,  there  is  a 
light  loss  due  to  the  expansion,  and  which  is  proportional  to  the 
expansion.  We  have  experimented  until  we  can  print  anamorphosed 
film  so  that  the  projected  image  appears  as  brilliant  as  ordinary 
screen  images.  Before  this  result  was  accomplished,  it  was  found 
possible  and  practicable  to  increase  the  arc  current  until  anamor- 
phosed and  ordinary  illumination  of  the  screen,  projected  consecu- 
tively from  different  machines,  appeared  equally  brilliant.  The 
Scott  Parrish  single  blade  superspeed  shutter  passing  about  50  per 
cent  more  light  without  flicker  by  decreasing  the  occulting  time,  and 
readily  adaptable  as  it  is  to  existing  projectors,  should  put  an  end  to 
any  necessity  of  increasing  light. 

The  cylindrical  anamorphoser  consists  of  a  positive  and  a  negative 
member  so  spaced  as  to  give  an  afocal  combination.  The  axes  of 
the  cylinders  are  parallel;  in  fact  strict  parallelism  is  essential. 

Jan.,  1933]  WIDE  SCREEN  PHOTOGRAPHY  39 

The  allowable  errors  in  alignment  are  almost  infinitesimal,  but 
mechanical  and  optical  means  for  rapidly  attaining  and  maintaining 
suitable  alignment  have  been  devised,  and  have  solved  what  at  first 
seemed  to  be  an  insuperable  obstacle  to  the  development  of  a  good 
objective.  Similarly,  means  have  been  found  of  grinding  and  polish- 
ing cylindrical  surfaces  so  that  they  can  be  made  as  easily  as  spherical 
surfaces  and,  as  with  the  latter,  to  any  degree  of  perfection  that  seems 
necessary  and  desirable .  Their  manufacture  is  not  in  any  sense  a  hand 
process.  The  quality  improves  when  the  lenses  are  made  in  series. 


Present-day  motion  picture  photography  and  projection  make  de- 
mands on  the  optical  equipment  that  can  be  properly  understood 
only  when  three  independent  stages  of  the  image-reproducing  process 
are  analysed  and  subjected  to  quantitative  measurement  and  inter- 
pretation. Thus  we  have  first  to  consider  the  quality  of  the  image 
on  the  negative  film,  an  image  that  is  carried  essentially  unchanged 
to  the  positive  film.  Then  the  image  must  be  projected  by  means 
of  an  optical  system  that  has,  as  we  shall  see,  certain  inherent  limita- 
tions. Lastly,  the  eye  perceives  the  screen  image  and  requires,  for  a 
subjective  sensation  of  sharpness  and  brilliance,  that  the  blurring  of 
the  details  of  the  image  shall  not  exceed  amounts  that  we  shall  later 
discuss  and  correlate  with  the  definition  obtainable.  As  the  first  step 
we  shall  consider  the  photographic  image. 


Practical  studio  lighting  conditions  and  emulsion  speeds  require 
the  use  of  relatively  large  aperture  lenses,  between  f/2  and  //3. 
This  means  that  the  apex  of  the  cone  of  light  forming  a  point  image 
on  the  film  embraces  a  rather  large  angle,  and  when  not  focused  on  the 
film  casts  thereon  a  circle  of  diffused  light  of  appreciable  size,  a  size 
also  proportionate  to  the  distance  of  the  apex  of  the  cone  from  the 
film.  In  order,  therefore,  that  there  may  be  a  reasonable  depth  of 
focus  and  sharpness  of  image,  the  focal  length  of  the  lens  must  be 
short.  This  necessity  is  not  avoided  by  using  larger  film. 

The  average  focal  length  used  for  general  purposes  is  50-mm.  or  2 
inches.  Shorter  focal  lengths  are  frequently  used,  for  instance  !3/8 
inches;  but  the  ability  of  most  lenses  to  cover  a  1-inch  field  at  a 
20  degree  semiangular  opening  with  sufficient  sharpness  is  partly  due 
to  the  absolute  decrease  in  the  dimensions  of  the  marginal  imagery 

40  H.  S.  NEWCOMER  [J.  S.  M.  P.  E. 

errors.  A  2-inch  lens  covering  a  1-inch  field  has  a  semiangular  open- 
ing of  14  degrees.  A  discussion  of  the  characteristics  of  the  images 
formed  by  such  lenses  will  serve  to  set  forth  the  conditions  under 
which  motion  picture  lenses  operate. 


It  has  not  been  an  easy  problem  to  design  lenses  that  will  give  satis- 
factory results  under  the  conditions  obtaining  in  motion  picture 
photography.  W.  Merte1  discusses  briefly  the  difficulties  with  which 
the  designer  of  such  objectives  is  faced.  One  of  the  methods  of 
approach  to  the  problem  is  to  modify  the  Petzval  objective  so  as  to 
flatten  its  field.  As  is  well  known,  this  objective  in  its  original 
form  has  a  large  aperture  and  an  unusually  sharp  central  definition 
for  a  lens  of  such  simple  construction.  The  definition,  however, 
rapidly  falls  off  and  is  unsatisfactory  even  for  short  focal  lengths  at 
the  margin  of  a  field  subtending  a  greater  semiangular  opening  than 
about  7  degrees,  requiring  thus  a  4-inch  lens  to  cover  a  standard 
frame.  (See  Fig.  6,  Solex  and  Cinephor.) 

A  second  modification  is  obtained  by  placing  a  strong  collective 
element  in  front  of  or  behind  suitably  designed  Taylor  triplets. 
See,  for  instance,  the  Ernostar  (Merte  No.  10/8)  and  the  Astro-Tachar 
(Merte  No.  11/8). 

A  third  modification,  semisymmetrical  in  type,  is  based  on  the  old 
Rudolph  Planar  which,  in  turn,  was  developed  after  Alvan  Clark's 
lens  of  1889  (U.  S.  Pat.  No.  399,499).  Each  half  has  a  strong  collec- 
tive element  in  front  of  a  compound  dispersive  element.  Examples 
of  this  are  seen  in  the  Xenon,  Ray  tar,  Biotar  (Merte  No.  14/8)  and  the 

Another  type  is  derived  from  a  symmetrical  lens  by  introducing 
into  each  half  a  dispersive  meniscus  turned  convex  toward  the 
diaphragm  (Merte  No.  7/8).  Such  lenses  having  large  apertures 
have  been  widely  used  for  amateur  photography,  but  they  cover 
only  a  small  field  and  show  considerable  spherical  aberration.  - 

Another  class  of  objectives  deserving  mention  are  those  triplets 
that  have  been  redesigned  to  increase  the  opening  to//3.5  or  more. 
Examples  are  the  Hypar  (similar  to  Merte  No.  11/3)  and,  particularly 
because  of  its  wide  angle,  the  Tessar  (Merte  Nos.  12/4,  13/4). 

The  quality  and  suitability  of  any  of  these  lenses  is  in  part  de- 
pendent upon  the  curvatures  of  their  focal  surfaces,  their  spherical 
aberrations  and  their  sine  condition  errors.  All  these  characteristics, 

Jan.,  1933]  WlDE  SCREEN  PHOTOGRAPHY  41 

for  a  great  many  lenses,  are  individually  set  forth  in  graphic  form 
in  Merte's  work  above  referred  to.  Whereas  the  graphs  for  the 
various  lenses  show  differences  that  must  be  associated  with  varia- 
tions in  their  image-forming  characteristics,  these  differences,  as 
between  the  more  important  examples,  are  of  less  significance  to  lens 
performance  than  other  features  more  readily  recognized  on  direct 

In  order  to  bring  out  the  limitations  of  all  these  lenses  and  to  show 
to  what  extent  they  are  being  utilized  to  their  maximum  capacity, 
a  short  description  of  their  individual  and  relative  performance 
characteristics  may  be  made. 


Figs.  6  and  7  show  two  sets  of  curves  illustrating  the  operating 
characteristics  of  a  number  of  the  more  important  motion  picture 
lenses.  Fig.  6  shows  the  form  of  the  two  focal  surfaces,  tangential 
and  sagittal  as  they  are  called,  of  four  photographic  lenses  and  four 
projection  lenses.  These  measurements  were  made  on  a  suitable 
optical  bench  with  a  cross  slide,  using  a  simple  ocular  to  locate,  on  a 
finely  ground  glass  mounted  on  a  vernier  slide,  the  best  focus  for 
tangential  and  radial  (sagittal)  lines  of  the  target,  at  different  angles 
of  the  target  away  from  and  at  right  angles  to  the  axis  of  the  lens. 
In  the  case  of  the  camera  lenses,  2-  or  3-inch  lenses  were  used  for  the 
measurements.  The  curves  show  where,  with  respect  to  the  focal 
plane,  the  best  focus  for  the  two  sets  of  lines  is  obtained.  The 
sagittal  surface  generally  lies  nearer  the  lens.  In  the  illustration,  in 
each  instance,  the  respective  surfaces  are  indicated  by  the  letters  S 
and  T.  The  unit  "one"  is  chosen  as  one  one-hundredth  part  of  the 
focal  length.  A  certain  approximation  of  the  two  curves  to  each  other 
and  to  the  focal  plane  is  necessary  for  good  definition,  but  the  exis- 
tence of  such  an  approximation  does  not,  unfortunately,  necessarily 
mean  that  there  is  good  definition.  Thus,  on  the  one  hand,  the 
quality  of  the  image  on  the  surface  may  be  poor;  or,  on  the  other 
hand,  there  may  be  a  fairly  good  image  at  some  distance  from  the 
surface.  A  comparison  of  the  curves  of  Fig.  6  with  those  for  blurring 
of  the  image  (Fig.  7)  will  show  a  correlation  between  the  two,  but 
the  latter  curves  more  accurately  indicate  the  quality  of  the  image 
on  the  film. 

Fig.  7  plots  for  each  lens  described  the  approximate  blurring  of  the 
image,  or  the  size  of  the  diffusion  circle  in  hundredths  of  a  millimeter 



[J.  S.  M.  P.  E. 

for  50-mm.  lenses,  //2.3  opening  (except  Tessar  f/2.7)  at  various 
semiangular  fields.  The  sizes  of  the  diffusion  circles  are  estimated 
from  inspection,  under  suitable  magnification,  of  images  of  bold- 
faced type  on  fine-grain  negatives.  In  general,  a  block-faced  letter 
must  be  a  little  over  2l/2  times  the  height  of  the  estimated  diffusion 
circle  to  be  legible,  although  words  are  legible  at  somewhat  less 
height.  Illegibility  may  be  due  to  a  number  of  imagery  defects. 
Thus,  there  may  be  mostly  simple  diffusion  of  the  image  as  with  the 




FIG.  6.  Sagittal  and  tangential  focal  surfaces  of  four  motion 
picture  camera  lenses  and  four  projection  lenses.  Ordinates  are 
semiangular  field;  abscissas  Vioo  focal  length. 

Xenon  or  Ray  tar;  or  marked  astigmatism  may  account  for  the 
illegibility,  as  in  the  case  of  the  Biotar  and  Tessar  intermediate  zone 

The  curves  of  Fig.  7  serve  to  help  one  to  visualize  the  more  par- 
ticular description  of  the  following  paragraphs,  and  also  to  correlate 
information  contained  therein  with  the  conditions  obtaining  on 
projection  of  the  image  on  the  screen,  a  problem  to  be  discussed 

Jan.,  1933] 



kThe  following  information  is  based  on  the  microscopic  examination 
fine-grain  Eastman  No.  40  and  Wratten  and  Wainwright  pan- 
chromatic emulsion  test  chart  plates,  Mazda  lighting,  using  posterior 
and  anterior  targets  to  control  the  focal  plane  setting  of  2-inch  lenses. 
Valuable  additional  information  was  obtained  by  the  direct  micro- 
scopic examination  of  free  aerial  images  using  microscope  objectives 
of  sufficient  aperture  to  take  in  the  entire  cone  of  light  traversing  the 
lens  aperture  and  forming  the  image.  This  latter  method  enables 




15"          2.0"         ab 
field,  standard 


FIG.  7.  Curves  for  five  2-inch  motion  picture  lenses 
and  for  the  corresponding  maximum  increment  of  diffusion 
due  to  the  simultaneous  use  of  an  anamorphoser  of  the 
type  described.  The  lateral  edges  of  the  image  fields  of 
standard  and  wide  film  are  indicated.  Ordinates  are  dif- 
fusion circles  in  Vioo-mm. ;  standard  as  described. 

one  instantly  to  appraise  the  image  quality  and  to  determine  ab- 
solutely the  performance  characteristics  at  the  center  of  the  field 
and  the  performance  possibilities  for  nonaxial  points  without,  how- 
ever, determining  whether  a  good  lateral  image  actually  lies  in  the 
Gaussian  plane.  The  method  is,  of  course,  most  productive  for 
those  who  are  in  the  habit  of  critically  examining  microscope  images. 
The  Tessar  f/2.7  is  an  example  of  a  large  aperture  lens  with  con- 
siderable covering  power.  The  50-mm.  lens  image  is  fairly  sharp 
at  the  edge  of  a  44-mm.  area,  24-degree  semiangular  field.  At  these 

44  H.  S.  NEWCOMER  [J.  S.  M.  p.  E. 

large  openings,  the  definition  of  the  central  and  intermediate  areas 
is  relatively  much  poorer  than  with  certain  other  types  of  lenses. 
In  fact,  in  an  intermediate  zone  from  12y2  to  20  degrees  there  is  a 
distinct  astigmatic  blurring  of  the  image  even  at  appreciably  smaller 
openings.  The  images  are  slightly  better  on  Eastman  No.  40  emul- 
sion than  on  panchromatic  stock.  As  the  Tessar  is  stopped  down  to 
f/4.5,  it  loses  some  of  its  relative  superiority  as  a  wide-angle  lens. 
Thus,  the  Xenon  gives  a  much  sharper  image  everywhere  up  to  about 
20  degrees.  The  very  slightly  greater  sharpness  of  the  Raytar  at 
large  angles  is  a  stopping-down  effect  accompanied  by  decreased 
illumination.  With  smaller  stops  (//4.5)  the  sharpness  of  the  mar- 
ginal image  increases  and  the  illumination  becomes  more  uniform. 

At//2.7  the  Xenon  is  quite  sharp  for  a  central  area  of  about  11 
degrees  semiangle;  and  at  f/3.2  it  has  nearly  reached  the  limit  of 
resolving  power  of  the  emulsion,  and  leaves  little  room  for  further 
improvement.  Even  stopping  it  to  //8,  for  instance,  extends  this 
area  of  extreme  sharpness  only  to  15  degrees,  and  without  much 
change  over  f/3.2.  The  Tessar  at  //8,  while  not  so  sharp  in  this 
region,  is  distinctly  better  to  the  edge  of  a  much  larger  field,  i.  e., 
beyond  about  18  degrees. 

The  Biotarf/lA  is  one  of  the  better  wide  aperture  lenses,  although 
it  does  not  give  images  of  the  quality  here  under  discussion  until 
stopped  down  to  apertures  equivalent  to  those  of  other  available 
lenses.  At  f/2  or  //2.3,  the  Xenon  is  somewhat  sharper  over  the 
central  area  and  is  quite  good  to  about  15  degrees,  whereas  the 
Biotar  falls  off  much  more  rapidly  beyond  10  degrees  but  improves 
again  beyond  15  degrees  to  be  better  for  a  narrow  peripheral  zone. 
As  the  stop  is  decreased  to  //4.5  and  smaller,  the  Biotar  maintains 
its  wide  angle  superiority  and  becomes  equal  to  the  best  lenses  at 
the  center.  The  Biotar  gives  slightly  better  images  on  No.  40  emul- 
sion, but  the  difference  does  not  amount  to  more  than  one  stop 
(//2.3  to//2.7). 

A  further  idea  of  the  relative  sharpness  of  the  images  of  these 
lenses  can  be  had  by  reference  to  Fig.  7.  In  this  connection  it  should 
be  noted  that,  for  instance,  the  Astro  Pan-Tachar  f/2.3  is  a  very 
popular  lens  for  motion  picture  work,  perhaps  because  it  lacks  a 
certain  degree  of  sharpness,  even  at  the  center,  so  that  there  is  less 
difference  across  the  field.  The  fields  of  both  the  Biotar  and  the 
Astro  Pan-Tachar  cut  off  sharply  at  about  22  degrees,  whereas  the 
Makro-Plasmat  has  a  very  wide  field  without,  however,  as  good  defini- 

Jan.,  1933]  WlDE  SCREEN  PHOTOGRAPHY  45 

tion  at  the  larger  angles,  beyond  6  degrees,  as  even  the  Astro  Pan- 
Tachar.  The  Makro-Plasmat,  when  stopped  down  to  //4.5,  has 
excellent  central  images  up  to  about  a  7-degree  demiangular  opening. 

Both  the  new  Raytar  f/2.3  and  the  Xenon  are  representatives  of  a 
type  of  lens  that  permits  the  attainment  of  high  speed  with  excellent 
definition.  Good  specimens  of  either  lens  in  50-mm.  focal  lengths 
and//2.3  opening  will  image  distinctly  in  the  visible  spectrum  over  a 
semiangular  field  of  5  degrees  a  one  four-hundredth  millimeter  break 
in  a  black  line  of  the  same  width.  At  10  degrees,  they  have  about 
one-half  and  at  15  degrees  one-fifth  this  resolving  power.  At  the 
center  it  is  nearly  twice  as  great.  By  way  of  comparison  the  resolving 
power  in  the  central  area  of  the  Astro  Pan-Tachar  as  viewed  in  the 
microscope  is  hardly  one-third  that  of  these  lenses. 

In  this  discussion  of  image  quality,  perfect  definition  as  judged  by 
the  microscope  corresponds  closely  to  the  maximum  observed  sharp- 
ness of  the  target  image  on  the  plate,  and  such  pictures  when  pro- 
jected with  suitable  lenses,  even  in  large  theaters,  show  extremely 
good  definition.  When  the  images  are  less  sharp,  the  difference  is 
noticeable  on  the  screen;  but  if  the  lighting  of  the  object  is  such  as 
to  give  "brilliance"  to  the  image,  less  sharp  definition  nevertheless 
gives  perfectly  satisfactory  images.  Thus  the  Astro  Pan-Tachar,  at 
f/2.3  with  suitable  lighting,  gives  brilliant  images  with,  however,  an 
observable  deterioration  toward  the  border  to  a  critical  eye. 


The  rate  of  deterioration  of  the  images  with  angle  is  for  many  of 
these  lenses  such  as  to  make  the  images  unsatisfactory  when  the 
angle  is  more  than  10  or  12  degrees  unless  the  focus  is  very  short. 
The  maximum  field  satisfactorily  covered  by  short  focus  wide  aper- 
ture lenses  is  22  degrees,  (28  millimeters  at  a  focal  length  of  35  milli- 
meters), and  then  only  with  a  certain  loss  of  quality  which  is  notice- 
able on  projection  if  details  are  to  be  pictured. 

When  the  focal  length  is  increased  to  50  millimeters,  the  standard 
movietone  frame  has  a  horizontal  semiangular  field  of  about  11V2 
degrees,  which  is  about  the  limit  to  which  most  lenses  still  give 
sufficiently  good  marginal  definition  not  to  detract  from  the  quality 
of  the  picture.  The  best  lenses  will  cover  satisfactorily  somewhat 
more  than  this,  but  even  on  the  new  50-mm.  wide  film  the  angle  is 
5Y2  degrees  greater,  and  then  the  lenses  available  are  either  appreci- 
ably poorer  at  the  border  or  show  an  intermediate  zone  of  blurring. 

46  H.  S.  NEWCOMER  [j.  S.  M.  P.  E. 

The  old  70-mm.  wide  film  carries  the  field  clear  out  to  25  degrees; 
and  it  is  obvious  from  the  data  given  here,  as  well  as  from  practical 
experience  with  such  film,  that  no  lens  covers  this  field  with  anything 
approaching  the  definition  attained  with  standard  film. 

Thus,  a  careful  study  of  the  properties  of  the  principal  sharply 
imaging  motion  picture  lenses  not  only  shows  their  individual  points 
of  superiority  and  the  absence  of  a  "universal"  lens,  but  makes  it 
quite  clear  that  definition  to  the  degree  now  attained  with  standard 
film  can  not  be  attained  on  substantially  larger  areas  if  equal  lens 
speeds  are  to  be  used.  On  the  other  hand,  wider  pictures  can  be 
optically  compressed  satisfactorily  into  the  area  in  which  good  images 
are  obtainable. 

Several  wide  film  pictures  were  shown  in  1930.  Opinions  as  to  the 
sharpness  of  the  images  in  these  pictures  vary  with  the  interest  and 
attention  of  the  observer  and  with  his  skill  in  taking  account  of  de- 
tail and  contrast  as  they  affect  apparent  definition.  Clever  com- 
position and  lighting  play  an  important  role  in  the  appearance  of  such 
pictures.  Certain  of  the  wide  film  pictures  shown  were  very  objec- 
tionally  lacking  in  portrayal  of  detail.  They  all  showed  distinct  loss 
of  definition  in  the  outer  portions  of  the  picture. 

It  seems  hardly  necessary  to  mention  here  the  very  poor  results 
obtainable  when  wide  screen  pictures  are  attempted  when  using  re- 
duced film  images  of  modified  shape  blocked  out  on  standard  film. 
Here,  as  was  amply  demonstrated  in  1930  and  as  could  have  been 
foreseen,  projection  difficulties  are  insurmountable. 


When  it  comes  to  projection  the  same  or  greater  difficulties  present 
themselves.  The  focal  lengths  are  longer,  4  to  7  inches,  and  in  order 
to  obtain,  with  a  suitable  aperture,  the  required  high  degree  of  central 
definition  needed  for  such  long  focal  lengths,  it  is  necessary  to  use 
lenses  of  the  Petzval  type  having  notoriously  limited  angular  fields. 
The  greatest  volume  of  light  is  probably  confined  to  an//3  projection 
aperture,  and  with  such  an  opening  the  central  images  of  the  best 
Petzval  lenses  are  on  direct  visual  examination  somewhat  less  sharp 
but  approximately  the  same  as  those  of  the  motion  picture  lenses  just 

The  actual  sizes  of  the  diffusion  circles  of  the  Petzval  lens  have 
been  the  subject  of  exhaustive  mathematical  analysis.  In  fact, 
it  would  not  be  proper  to  leave  this  subject  without  reference  to  the 

Jan.,  1933]  WlDE  SCREEN  PHOTOGRAPHY  47 

classical  paper  by  K.  Schwarzschild  on  the  astrophotographic  objec- 
tive.2 Such  an  objective  may  be  defined  as  one  in  which  the  area 
to  be  sharply  covered  is  not  greater  than  the  diameter  of  the  objec- 
tive, a  condition  that  holds  in  motion  picture  photography  and 
projection  with  lenses  of  3-inch  focus  and  longer.  Taking  account 
of  third  order  terms,  Schwarzschild  gives  a  complete  mathematical 
analysis  of  the  resolving  powers  of  such  lenses  and  evaluates  the 
theoretical  minimum  attainable  diffusion  of  their  images. 

As  is  well  known,  the  expansions  of  expressions  for  the  aberrations 
of  spherical  objectives  contain  only  odd  order  terms,  and  it  has  not 
yet  been  possible  to  derive  solutions  in  which  fifth  or  higher  order 
terms  are  retained.  Probably  such  derivations  are  beyond  the 
capacity  of  the  human  mind.  They  seem  to  be  unnecessary  when  cer- 
tain restrictions  on  aperture  and  curvature  of  glass  surfaces  are  made. 

The  motion  picture  lenses  of  larger  aperture,  having,  as  some  or  all 
of  them  do,  large  curvatures  of  the  glass  surfaces,  represent  empirical 
solutions  of  the  problem  controlled  by  laborious  trigonometric  cal- 
culations. While  generalizations  should  not  be  made,  it  is  probable 
that  the  more  or  less  uniformity  in  the  marginal  image  defects  shown 
by  the  best  of  these  lenses  is  an  expression  of  the  minimal  expectable 
residuum  of  third  and  fifth  order  aberrations.  Thus,  where  large 
openings  and  a  high  degree  of  central  definition  are  required,  the 
further  addition  of  surfaces  has,  as  we  have  seen,  reduced  the  aberra- 
tions outside  the  axis  so  as  to  extend  the  field  slightly  and  at  the 
same  time  give  the  advantage  of  increased  openings  with  practical 
limits  of  about //2. 3.  (Compare  for  instance,  in  Fig.  6,  the  first  three 
lenses  in  the  second  line  with  the  other  lenses.) 

Every  useful  objective  must  be  achromatic,  i.  e.,  color  corrected 
for  two  particular  wavelengths.  The  residual  lack  of  color  correc- 
tion for  the  intervening  wavelengths  is  called  the  secondary  spectrum 
of  the  lens,  and  in  the  useful  spectral  interval  reaches  a  maximum  at  a 
certain  wavelength.  This  color  error  of  the  astrophotographic  objec- 
tive is  for  the  center  of  the  field  the  worst  error  that  it  has;  and 
however  small  other  errors  may  be,  they  will  be  hidden  in  the  color 
diffusion  circle.  The  latter,  therefore,  even  if  somewhat  better 
tolerated,  furnishes  a  criterion  for  the  measurement  of  other  errors. 
Schwarzschild  has  shown  that  this  color  error  has  a  minimum  theoreti- 
cal value,  which  may  be  expressed  in  terms  of  the  size  of  the  resulting 
diffusion  circle  in  the  focal  plane  of  the  objective,  this  circle  sub- 
tending an  arc  of  33"  v,  where  v  is  the  diameter  of  the  lens  opening, 

48  H.  S.  NEWCOMER  [J.  S.  M.  P.  E. 

with  a  diameter  of  //10  taken  as  unity.     For  a  narrow  spectral  range, 
as  in  projection,  this  figure  can  be  at  least  halved. 

It  is  hardly  necessary  to  mention  that  objectives  comprised  of 
thin  unspaced  glasses,  as  in  telescopes,  show  considerable  astigmatism 
and  curvature  of  the  image  fields.  In  fact  if  g  represents  the  semi- 
angular  opening  of  the  image  field,  with  3  degrees  taken  as  unity, 
then  the  two  diameters  of  the  diffusion  circle  of  such  lenses  are 
104"  g*v  and  47"  g*v,  respectively. 

By  separation  of  the  elements,  curvature  of  the  field  and  coma  can 
be  eliminated;  and  if  one  adheres  to  the  Petzval  type,  the  greatest 
theoretical  reduction  in  the  diffusion  circle  due  to  astigmatism  is 
to  9"  g^u.  When  we  come  to  build  such  lenses,  12"  g^u  seems  to  be 
the  practical  lower  limit.  The  lenses  have,  however,  the  theoretical 
lower  limit  for  the  secondary  spectrum,  namely,  33" v. 

In  Fig.  6  are  shown  the  positions  of  the  tangential  and  sagittal 
image  surfaces  of  two  types  of  Petzval  lenses.  The  Cinephor  was 
selected  for  this  discussion  because  it  is  an  example  of  the  most  com- 
mon type  of  Petzval  construction  in  projection  lenses.  It  has  con- 
siderable astigmatism,  but  the  average  curvature  of  the  field  is  not  far 
from  zero.  A  drawing  is  included  of  a  Cinephor  of  later  manufacture 
having,  up  to  nearly  5  degrees,  no  astigmatism  and  a  very  flat  field. 
Another  type  is  illustrated  by  the  Solex  lens.  The  Solex,  although 
having  an  appreciable  curvature  of  field  beyond  5  degrees,  up  to 
that  point  has  little  curvature  and  less  astigmatism  and  gives  ex- 
cellent images  with  standard  film  in  the  usual  focal  lengths. 

In  all  instances  curves  for  41/2-inch  projection  lenses  are  given.  In 
motion  picture  projection,  the  size  of  the  field  to  be  projected  remains 
constant  regardless  of  the  focal  length  of  the  lens;  hence  the  de- 
signers of  projection  lenses  have  been  under  no  obligation  to  make  all 
focal  lengths  geometrically  similar,  such  as  is  generally  done  in  the 
case  of  ordinary  photographic  lenses  where  plate  size  is  proportional 
to  focal  length.  The  values  given  for  the  Solex  and  Cinephor,  there- 
fore, can  not  be  regarded  as  strictly  applicable  to  all  lenses  bearing 
those  names,  although  they  give  a  correct  impression  as  to  their 
characteristics.  Likewise,  the  focal  surface  characteristics  of  cer- 
tain motion  picture  camera  lenses  vary  with  the  focal  length. 

The  Taylor  type  of  objective,  with  three  spaced  elements  and  some- 
what greater  curvatures  of  the  glass  surfaces,  can  be  designed  with 
appreciably  smaller  diffusion  circles  due  to  astigmatism,  but  the 
secondary  spectrum  increases  to  about  51  "v. 

Jan.,  1933]  WIDE  SCREEN  PHOTOGRAPHY  49 

Let  us  now  evaluate  these  expressions.  A  4V2-inch  projection  lens 
has  a  horizontal  semiangular  field  on  movietone  film  of  about  5 
degrees.  The  useful  opening  is  probably  not  over  //3.3.  Thus 
v  is  3,  g  is  1.67,  gz  is  2.8,  and  g*v  is  8.4.  The  lens  being  of  the  Petzval 
type,  its  diffusion  circle  at  the  margin  is  about  100  seconds  or  0.055 
millimeter.  Its  color  diffusion  circle  at  the  center  is  probably  about 
10" 'v  or  0.017  millimeter.  Both  these  figures  correspond  very  well 
to  the  observed  tolerances  and  direct  observation  on  good  lenses. 
The  figure  for  the  margin  is  usually  a  little  larger. 

The  result  of  projection  is  then  to  deteriorate  still  further,  but 
to  an  unimportant  extent,  the  central  image.  The  legibility  of  de- 
tails in  the  projected  image  is  within  the  tolerances  to  be  discussed. 
The  deterioration  of  the  marginal  image  of  the  standard  frame  is  of 
more  consequence,  but  is  still  just  allowable.  If,  however,  a  Petzval 
lens  were  used  to  cover  the  frame  of  50-mm.  wide  film,  g2  becomes 
three  times  as  large  and  the  marginal  diffusion  circle  is  0.165  milli- 
meter. As  we  shall  see,  this  is  too  large.  To  project  such  pictures, 
other  lenses  must  be  used.  Unfortunately,  it  is  not  easy  to  find  a 
substitute.  The  use  of  an  anamorphoser  is  a  much  simpler  solution. 


We  should  now  consider  these  numerical  data  in  the  light  of  the 
observed  image  on  the  screen.  The  center  of  a  sharp  motion  picture 
negative  or  positive  will  show  distinctly  letters  formed  by  lines 
0.01  to  0.02  millimeter  wide.  Letters  that  are  0.1  millimeter  high  on 
the  film  may  be  nearly  illegible  without  one's  noticing  loss  of  detail 
when  the  picture  is  projected.  In  a  theater  with  a  100-foot  throw 
and  a  25-foot  picture,  such  a  letter  is  about  30  millimeters  high  on 
the  screen.  At  a  distance  of  40  feet  from  the  screen,  the  average 
person  with  good  vision  can  read  letters  20  millimeters  high,  but  he 
does  not  try  to  exercise  his  vision  to  this  extent  and  can  not  distinguish 
the  coarser  details  of  the  letters  until  they  are  about  80  millimeters 
high,  the  distinguishable  details  then  having  dimensions  of  about  10 

Probably  the  average  critical  observer  does  not  notice  extreme 
haziness  of  letters  that  are  0.1  millimeter  high  on  the  film.  Even  their 
being  illegible  may  not  be  noticed,  so  that  what  has  here  been  called 
a  0.04-mm.  diffusion  circle  would  be  just  tolerated  at  the  center  of 
the  picture.  This  size  of  diffusion  circle  would  be  quite  satisfactory 
at  the  border,  and  nearly  twice  that  size  would  be  tolerated  provided 

50  H.  S.  NEWCOMER  [j.  S.  M.  P.  E. 

projection  did  not  make  matters  worse.  The  figure  0.055  millimeter 
given  above  for  projection  is  perhaps  not  to  be  added  in  its  entirety 
to  the  size  of  the  diffusion  circle  at  the  margin  of  the  negative  image 
(Fig.  6)  but  the  combined  effect  must  be  just  about  what  has  been 
considered  allowable. 

In  order  to  visualize  the  meaning  of  these  figures  one  might  hold 
an  inside  page  of  the"  New  York  Times  at  arms  length.  The  "want 
ads"  will  be  just  legible.  The  individual  letters,  even  if  jumbled, 
would  also  be  legible  if  they  were  distinctly  formed.  Such  letters 
correspond  to  the  20-mm.  screen  letters  of  the  above  example  or  to 
0.07-mm.  film  letters.  Even  the  very  best  lenses  will  not  reproduce 
such  characters  sharply;  and,  indeed,  the  reader  in  looking  over  the 
newspaper  at  arms  length  does  not  attempt  to  notice  print  of  that 
size.  He  is  not  even  attentive  to  the  ordinary  newsprint,  which  is 
half  again  as  large.  On  the  other  hand,  letters  40  millimeters  high 
on  the  screen — 0.14  millimeter  on  the  film,  for  which  our  diffusion 
circle  is  0.05  millimeter — correspond  to  minor  titles  in  the  news 
column,  which  may  very  well  be  read  if  the  attention  be  attracted 
to  them.  In  sharp  film  they  will  be  legible,  but  not  as  clear  as  in 
the  news  print  analogy.  The  80-mm.  screen  letters,  appearing  sharp 
or  at  least  clear,  as  they  do  in  good  pictures,  correspond  roughly  to 
the  column  headings  in  the  newspaper.  They  must  appear  distinct  if 
even  the  casual  observer  is  to  be  satisfied.  While  such  letters  are 
sharp  at  the  center  and  distinct  to  the  edge  of  standard  film,  a  com- 
parison with  the  curves  of  Figs.  6  and  7  shows  that  they  would  be 
just  about  illegible  in  the  peripheral  areas  of  wide  film  no  matter  what 
lens  were  used. 

Anamorphosed  or  compressed  negative  motion  picture  images 
are  obtainable  in  actual  practice  in  which  there  is  perfect  definition 
of  letters  appearing  even  at  the  margin  of  the  picture  and  of  sizes 
down  to  0.14  millimeter  high  on  the  film.  Such  letters  to  be  sharp 
mean  diffusion  circles  appreciably  less  than  0.04  millimeter  on  the 
film.  In  practice,  letters  that  are  0.04  millimeter  high  on  the  film 
are  illegible,  the  amount  of  illegibility  fixing  the  diffusion  circles  in 
the  central  area  at  about  0.02  millimeter,  corresponding  therefore 
with  the  data  of  Fig.  7. 

Referring  to  Fig.  6,  it  should  be  remembered  that  the  projection 
lens  works  at  twice  the  focal  length  of  the  typical  camera  lens  we 
have  been  considering.  The  diffusion  referable  to  the  curvature  of 
the  image  fields  shown  for  the  Solex  and  Cinephor  projection  lenses 

Jan.,  1933]  WlDE  SCREEN  PHOTOGRAPHY  51 

should  be  doubled  when  making  comparisons  with  the  data  for  the 
camera  lenses.  The  projection  lens,  however,  when  used  on  standard 
film,  is  required  to  cover  at  most  a  semiangular  field  of  only  5  degrees, 
and  under  such  conditions  does  fairly  well.  It  is  extremely  poor  at 
10  degrees  and  useless  beyond  and,  indeed,  before  10  degrees. 

Where  wide  angle  projection  is  necessary,  it  is  possible  to  better 
the  performance  of  the  Petzval  lens.  Reference  will  not  be  made 
here  to  back  screen  projection  where  both  the  focal  length  and  throw 
are  short  and  the  screen  image  less  sharp  than  in  standard  practice. 
We  have  seen  that  attempts  to  improve  lenses  that  perform  similarly  to 
the  Petzval  lens  have  resulted  in  the  development  of  the  present  motion 
picture  camera  lenses.  In  the  case  of  the  best  motion  picture  lenses 
above  described,  working  at  //2.3  or  //2.7  for  4V2-inch  focus,  the 
diffusion  circles  at  the  center  of  the  image  for  the  visible  spectrum 
are  about  0.004  to  0.01  millimeter.  Letters  0.05  millimeter  high  on 
the  film  are  quite  legible  and  sharp.  On  the  other  hand,  at  a  semi- 
angular  field  of  8  or  10  degrees  and  for  this  focal  length,  the  diffusion 
circles  are  about  0.04  millimeter  or  more. 

The  Super  Cinephor  is  an  example  of  a  camera  lens,  the  Raytar, 
adapted  to  projection  purposes.  In  Fig.  6  are  given  the  forms  of  its 
image  surfaces.  (The  6"  Raytar  has  similar  but  still  more  curved 
surfaces,  particularly  the  sagittal  surface.)  There  is  a  distinct  flatten- 
ing at  the  larger  angles  as  compared  with  the  Petzval  type  lenses. 

By  way  of  comparison,  the  hand  camera  anastigmat  working  at 
considerably  smaller  openings  seeks  to  limit  the  diffusion  at  a  semi- 
angular  field  of  about  30  degrees  to  120  seconds.  The  central  defini- 
tion is  not  as  good  as  with  the  lenses  here  under  discussion.  Great 
skill  and  effort  have  been  expended  in  an  endeavor  to  improve  the 
marginal  definition  of  all  of  these  lenses.  The  limits  reached  are 
fairly  well  defined  and  the  underlying  mathematical  concepts  do  not 
offer  much  encouragement  that  the  results  already  achieved  will  be 
much  extended. 

It  has  been  shown  that  it  is  not  possible  to  take,  nor  is  it  feasible 
to  project,  wide  screen  pictures  under  conditions  that  will  result 
in  images  half  as  good  as  those  now  obtained.  On  the  other  hand, 
wide  screen  pictures  of  a  quality  comparable  with  the  present  stand- 
ard pictures  may  be  obtained  by  using  an  anamorphoser.  The 
simplicity  of  this  method  of  projecting  wide  screen  pictures  hardly 
needs  to  be  elaborated  upon.  One  further  advantage  of  the  anamor- 
phoser should,  however,  be  mentioned.  This  is  an  optical  advantage. 

52  H.  S.  NEWCOMER  [J.  S.  M.  P.  E. 

increasing  the  depth  of  focus,  and  hence  the  general  sharpness  of  the 
images,  over  and  above  that  of  ordinary  pictures. 


A  cylindrical  anamorphosing  system  magnifying  50  per  cent  in  one 
meridian  increases  the  depth  of  focus  in  that  meridian  by  100  per  cent. 
If  the  anamorphoser  be  focused  for  a  given  object  distance,  then  the 
interaction  of  the  two  elements  of  the  anamorphoser  on  light  com- 
ing from  points  nearer  and  further  away  is  such  as  to  approximate  the 
corresponding  camera  lens  images  and  bring  them  nearer  the  image 
plane  for  the  mean  focus.  The  amount  they  are  moved  toward 
this  plane  is  exactly  one-half  the  focusing  difference  for  the  camera 

For  reasons  associated  with  the  nature  of  image  formation  in  the 
eye,  the  effect  of  natural  diagonal  astigmatism,  the  apparent  gain 
in  depth  of  focus  is  practically  equivalent  to  these  figures.  In  fact, 
all  who  have  studied  anamorphosed  wide  screen  pictures  have  noticed 
this  effect.  Similarly,  for  physiological  reasons,  the  expansion  in 
one  meridian  only  does  not  increase  the  graininess  of  the  projected 
image.  The  pictures  are  as  smooth  and  free  from  graininess  as  un- 
expanded  pictures  two-thirds  the  size. 

Up  to  this  point  we  have  considered  only  the  quality  of  the  image 
in  the  plane  of  best  focus.  Nothing  has  been  said  as  to  the  loss  of 
definition  due  to  the  photographing  of  portions  of  the  object  lying  in 
front  of  or  behind  the  plane  of  sharpest  focus. 

The  following  table  gives  the  focal  distances  for  a  certain  series 
of  lenses  when  the  object  is  at  15,  20,  and  25  feet.  The  last  two 
lines  of  the  table  give  the  focal  differences  with  respect  to  the  mean 
image  for  the  20-foot  distant  object. 

Focal  Distances  of  a  Lens  Series 



























diff.  in 






diff.  out  0.08  0.20  0.30  0.532  0.8 

The  relative  openings  being  the  same  in  each  case,  the  sizes  of  the 
diffusion  circles,  due  to  distances  out  of  focus,  of  the  objects  in  front 

Jan.,  1933]  WlDE  SCREEN  PHOTOGRAPHY  53 

and  back  of  the  sharply  imaged  object  are  directly  proportional  to 
these  distances.  Thus,  if  the  focal  length  of  the  lens  be  doubled, 
the  figures  show  that  the  loss  of  definition  due  to  decreased  depth  of 
focus  is  increased  four  times. 

Consider  the  deterioration  of  the  image  of  a  50-mm.  lens  due  to 
depth  in  the  object,  as  given  in  the  example.  For  the  lesser  of  the 
two  differences  it  amounts  to  a  diffusion  circle  of  0.04  millimeter. 
Diffusion  circles  this  large  (and  many  are  even  larger)  all  over  the 
film  area  cause  the  quality  of  the  picture  to  deteriorate  to  an  appreci- 
able extent.  The  anamorphoser  reduces  these  diffusion  circles  to 
half,  and  does  much  to  improve  the  actual  operating  quality  of  the 
image  and  bring  it  within  figures  comparable  with  those  given  for  the 
plane  of  best  focus,  as  for  instance  in  the  data  of  Fig.  7. 

For  cameras,  combination  motion  picture  lens  and  anamorphoser 
mounts  make  focusing  a  single  operation,  as  simple  as  in  ordinary 
practice.  For  the  theater,  a  simple  fixed  mount  can  be  devised  which 
reduces  both  costs  and  adjustments,  and  permits  rough  handling. 
Orientation  of  the  anamorphoser  in  the  proper  meridian  is  so  simple 
that  any  child  could  accomplish  it. 

Thus,  the  optical  and  practical  advantages  of  the  anamorphoser  are 
real  and  important.  Its  use  will  greatly  facilitate  the  introduction 
of  wide  screen  pictures  with  their  many  advantages  for  improved 
pictorial  effect,  pleasing  proportions,  and  increased  number  of  full- 
length  characters  on  the  screen.  In  the  latter  case,  the  increase  in 
size  of  the  object  imaged,  an  increase  allowed  by  the  altered  propor- 
tions of  the  frame,  still  further  increases  the  apparent  sharpness  of 
the  picture.  This  effect  can  not  be  ignored,  particularly  in  color 
photography,  where  there  is  a  certain  inherent  lack  of  definition  that 
this  application  of  the  anamorphoser  will  overcome,  and  without 
interfering  with  the  technic  of  the  color  process. 


1  MERTE,  W.:    "Construction  Types  of  Photographic  Objectives,"  Handbuch 
der  Wissenschaftlichen  und  Angewandten  Photographic  (Vol.  I,  The  Photographic 
Objective),  Vienna  (1932),  p.  243. 

2  Abhand  d.  Koniglichen  Gesellschaft  d.  Wissenschaften  zu  Gottingen.  Math. 
Phys.  Klasse,  New  Series,  IV  (1905),  No.  3. 


D.  R.  WHITE** 

Summary. — The  characteristics  of  Infra  D  film,  a  stock  designed  specifically  for 
specialized  cinematography,  possessing  distinctive  spectral  sensitivity,  are  described. 
The  sensitivity  is  limited  to  two  regions  at  opposite  ends  of  the  spectrum,  a  relatively 
wide  gap  occurring  between.  Examples  of  the  use  of  the  film  in  producing  special 
pictorial  effects  are  given  in  the  illustrations. 

Infra  D  film  is  a  stock  specially  designed  to  meet  the  requirements 
of  some  of  the  specialized  work  of  cinematographers.  Its  widest  use 
is  in  the  simulation  of  moonlight  effects,  but  it  has  also  been  used  for 
taking  pictures  through  aerial  haze. 

The  utility  and  special  properties  of  this  film  are  based  funda- 
mentally upon  its  distinctive  spectral  sensitivity.  Fig.  l(a)  shows 
that  this  sensitivity  is  effectively  restricted  to  two  regions  at  opposite 
ends  of  the  visible  spectrum  with  a  relatively  wide  gap  between. 
The  film  is,  therefore,  "green  blind,"  so  that  it  can  not  be  used  where 
true  reproduction  of  visual  brightness  values  is  desired. 

The  sensitometric  characteristics  of  Infra  D  are  shown  by  the 
curves  of  Figs.  2  and  3.  These  curves  resulted  from  rocked  tray 
developments,  in  borax  developer,  of  the  film  as  exposed  in  a  non- 
intermittent  time  scale  sensitometer,  in  which  the  light  source  was  an 
unscreened  incandescent  lamp  operated  at  a  color  temperature  of 
2475° K.  The  crosses  of  Fig.  3  give  time-gamma  values  for  du  Pont 
special  panchromatic  negative  processed  with  the  Infra  D,  and  show 
that  the  two  stocks  are  very  similar  in  their  development  behavior. 
Thus,  the  Infra  D  introduces  no  new  processing  difficulties,  and  can 
be  handled  along  with  other  negatives. 

Further  information  concerning  its  sensitometric  characteristics 
and  its  spectral  sensitivity  is  contained  in  the  group  of  curves  of  Fig. 
4  and  the  spectrograms  of  Fig.  1.  The  spectrograms  made  through 
the  filters  were  not  all  exposed  for  the  same  time,  but  the  times  were 

*  Received  by  the  editor  Oct.  24, 1932. 
**  Du  Pont  Film  Mfg.  Co.,  Parlin,  N.  J. 



adjusted  to  agree  partially  with  the  increased  exposure  that  would  be 
required  in  practice  and  to  emphasize  pictorially  the  effective  spectral 
regions.  The  sensitometer  lamp  was  screened  in  turn  by  each  of  the 
series  of  filters  used  in  making  the  spectrogram  and,  in  addition, 
with  the  Wratten  green  or  B  filter.  The  spectrograms  show  the 


FIG.  1.     Spectrograms    on    Infra    D    film,  exposed    to 

incandescent   light   unscreened   and   screened  by   various 

Wratten  niters:     a,  unscreened;    b,  K3  filter;  c,  A  filter; 
d,  F  filter;   e,  70  filter;   f,  88  filter. 

nature  of  the  light  that  was  effective  through  each  of  the  filters, 
and  the  curves  show  s'ensitometric  characteristics  of  the  film  as 
exposed  to  that  light.  The  relative  placing  of  the  curves  along  the 
log  E  axis  is  related  to  the  filter  factors  for  the  various  filters  with 
that  illumination,  the  displacement,  in  logarithmic  units,  of  any 
curve  from  the  white  light  curve  being  the  logarithm  of  its  filter 


D.  R.  WHITE 

[J.  S.  M.  P.  E. 

factor.  The  extreme  displacement  of  the  curve  with  the  green  or 
Wratten  B  filter  emphasizes  again  the  low  green-sensitivity  of  the 
film.  The  gamma  value  obtained  with  the  film  depends  upon  the 


FIG.  2.     H  &  D  curves  for  different  development  times 
on  Infra  D  film. 

character  of  the  light  incident  upon  it,  being  greater  for  red  than  for 
white  light. 

The  increased  contrast  resulting  from  red  light  exposure  can  be 





Dty  Time- Mm. 

u  2  4  6  8  '0  iz 

FIG.  3.  Time  gamma  curve  for  Infra  D  film.  Borax 
developer  was  used,  rocked  in  a  tray.  The  crosses  show 
gamma  values  from  du  Pont  special  panchromatic 
negative  developed  at  the  same  time. 

put  to  very  practical  use  in  photographing  through  haze,  when 
sufficient  exposure  can  be  given.  The  red  filter  aids  in  obtaining 
detail  through  the  haze,  the  greater  contrast  also  increasing  its 

Jan.,  1933] 



visibility  in  the  finished  picture.  Fig.  5  shows  two  pictures  taken 
from  an  elevated  point  of  land  looking  over  miles  of  lowland  on  a 
day  when  haze  was  noticeably  present.  The  rendering  of  detail  in 
the  picture  taken  through  the  red  filter  far  surpasses  that  of  the 

FIG.  4.  H  &  D  curves  of  Infra  D  film  exposed  to  white 
light  and  to  light  screened  by  the  various  Wratten  filters 

picture  taken  with  no  filter;  and,  in  fact,  surpasses  that  of  other 
test  pictures  made  at  the  time  using  different  filters  and  different 
types  of  film.  The  greater  detail  is  due  both  to  the  penetration 

FIG.  5.     Pictures  taken  from  an  elevated  point  of  land:     left,  no  filter  on 
panchromatic  film;  right,  70  filter  on  Infra  D. 

of  the  red  light  through  the  hazy  atmosphere  and  to  the  greater 
contrast  of  the  film  due  to  the  fact  that  the  latter  was  exposed  to  red 

The  photographs  shown  in  Fig.  6  (a,  b)  and  Fig.  7  are  pictorial 

58  D.  R.  WHITE  [j.  S.  M.  P.  E. 

in  character,  intended  to  typify  some  of  the  possibilities  of  the  stock 
and  to  show  the  results  to  be  expected  from  some  of  the  filters  fre- 
quently used  with  it. 

FIG.  6 (a).  FIG.  6(b). 

FIG.  6.  Pictures  taken  on  Infra  D  film  in  bright  sunlight  on  a  July  afternoon, 
printed  on  the  same  grade  of  paper:  (a)  no  filter;  (b)  F  filter.  A  K3  filter  pro- 
duces an  appearance  intermediate  between  those  of  (a)  and  (b);  A,  70  and  88 
filters  produce  effects  somewhat  similar  to  those  of  (b)  when  the  proper  filter 
factors  are  used. 

FIG.  7.  Picture  made  from  same  negative  as  those  of 
Fig.  6,  but  with  different  technic,  particularly  in  the 
printing  and  selection  of  paper. 

The  filter  factors,  in  bright  sunlight,  are  given  in  the  table  below: 

Filter  Factor 

Kt  16 

A  64 

F  64 

70  64 

88  90 

Jan.,  1933]  INFRA  D  NEGATIVE  EFFECTS  59 

These  were  used  in  obtaining  the  pictures  shown,  and  are  designed 
to  give  pictures  of  very  similar  overall  density.  The  pictures,  Fig. 
6  (a,  b),  were  both  printed  on  the  same  grade  of  paper,  and  show  the 
relative  changes  produced  by  the  niters.  The  pictures  were  taken 
on  a  bright  July  afternoon,  but  those  taken  with  red  niters,  of  which 
6(b)  is  typical,  resemble  snow  scenes  as  they  are  printed.  Fig.  7 
resulted  from  printing  the  negative  used  for  Fig.  6(b)  on  a  softer 
grade  of  paper;  resulting,  in  this  case,  in  quite  a  satisfactory  night 
picture.  It  is  sometimes  desirable  somewhat  to  underexpose  such 
pictures  in  order  to  suppress  shadow  detail,  or  to  underdevelop  the 
negatives  slightly  so  as  to  obtain  the  desired  effect.  The  extent  to 
which  these  methods  are  used  depends  upon  the  final  effect  desired. 
The  dark  sky  and  sharply  defined  shadows  of  night  can  be  thus 
simulated  in  bright  sunlight.  Care  must  be  used  to  have  the  rest  of 
the  atmosphere  correct,  of  course,  since  windows  and  streetlights 
are  often  lighted  at  night  but  rarely  in  the  daytime,  and  omission 
of  these  details  might  be  fatal  to  the  effect. 

The  limits  of  the  use  of  this  stock  have  by  no  means  been  reached. 
Trial  and  study  by  the  users  of  the  film  will  surely  lead  to  unique  and 
beautiful  effects  not  touched  on  here. 



Summary. — Several  precautions  must  be  observed  when  variable  density  sound 
records  are  produced  on  35-mm.  lenticular  film.  An  ammoniacal  glycine  solution 
is  considered  the  most  satisfactory  developer.  In  order  to  secure  the  necessary  indi- 
vidual control  of  the  picture  and  sound  records,  it  is  suggested  that  the  picture  record 
be  developed  in  a  devoloper  sufficiently  charged  with  bromide,  reversed,  and  then 
bleached,  cleared,  and  dried.  The  sound  record  should  then  be  exposed  on  the 
slightly  sensitive  emulsion  remaining,  and  the  entire  film  then  developed,  fixed, 
washed,  and  dried. 

For  better  sound  reproduction  it  is  also  suggested  that  the  height  of  the  embossed 
lines  in  the  sound  track  area  be  less  than  that  in  the  picture  area. 

In  considering  the  future  of  motion  pictures  in  color,  with  the  so- 
called  lenticular  films,  it  appears  probable  that  their  introduction 
into  the  industry  will  demand  certain  precautions.  From  an  optical 
point  of  view  it  should  be  possible  to  avoid  the  reversal  process,  but 
at  present  it  is  necessary  to  use  this  method. 

In  the  opinion  of  the  writer,  the  application  of  the  process  to  35-mm. 
film  would  benefit  by  the  use  of  CapstarFs  methods  with  respect  to 
the  second  exposure1  since  the  reversal  process  using  a  solvent  de- 
veloper is  a  difficult  one  which  requires  control  in  the  second  ex- 
posure and  development. 

If  a  reversed  image  in  colors  be  made  in  silver  bromide,  the  gamma 
can  easily  be  measured,  and  it  appears  that  the  development  of  the 
second  exposure  to  gamma  infinity  does  not  always  give  the  best 
colored  image. 

The  loss  of  color  in  the  reproduction,  as  compared  with  the  original, 
can  be  put  at  approximately  15  per  cent  of  the  quality  and  the  ac- 
curacy of  the  subject.  Attention  is  called  to  the  fact  that  an  original 
on  35-mm.  lenticular  film  has  never,  in  the  writer's  experience,  been 
made  according  to  Capstaff's  methods.**  We  may,  therefore,  infer 

*  Technical  Director,  Tobis  Sound  Films,  Paris,  France. 

**  Since  the  preparation  of  this  article,  such  films  have  been  projected  before 
the  Society. 


it  in  the  majority  of  cases  the  original  that  was  to  be  reproduced 
was  not  the  best  one  that  could  be  obtained. 

A  striking  example  can  be  found  by  considering  the  scales  of  blue 
and  red  colors.  It  is  clear  that  the  curve  after  the  second  develop- 
ment does  not  differentiate  between  a  deep  navy  blue  and  black,  and 
that  the  maximum  density  between  black  and  blue  varies  within  very 
narrow  limits. 

On  the  other  hand,  in  reproduction,  the  "antidiffusing  power" 
of  the  developer  that  is  used  for  the  first  development  must  be  taken 
into  account.  The  "antidiffusing  power"  of  a  developer  is  a  func- 
tion of  its  reduction  potential.  The  lower  the  reduction  potential 
the  less  is  the  "diffusion,"  and  the  better  is  the  definition.  Hundreds 
of  tests  have  shown  that  the  ammoniacal  glycine  developer  (Richard's 
formula)  is  one  of  the  best  for  the  lenticular  process,  since  glycine  has 
in  this  developer  a  very  low  potential,  which  approaches  the  desired 

By  photographing  a  white  surface  with  lenticular  film  and  using 
the  reversal  process,  a  film  is  produced  in  which  the  centers  of  the 
fields  behind  the  lenticular  elements  are  clear  and  the  interspaces  are 
black.  If  a  silver  salt  be  precipitated  in  the  gelatin  layer  of  this 
film,  an  emulsion  of  very  fine  grain  with  artificially  darkened  inter- 
spaces is  produced.  After  the  exposure  of  such  a  film  in  the  camera  it 
is  possible  to  develop  without  reversal  by  means  of  an  amidol  de- 
veloper and  thus  to  produce  a  negative  image  in  brilliant  colors, 
demonstrating  the  role  played  by  "diffusion." 

The  best  developer  is  made  according  to  the  Lippman  formula, 
which  is  used  for  interferential  photography;  but  this  formula  can  not 
be  recommended  owing  to  its  tendency  to  form  dichroic  fog. 

The  preventing  of  moire*  pattern  in  optical  printing  does  not  result 
in  the  same  sharpness  as  is  obtained  in  contact  printing.  It  is 
necessary  to  accept  a  much  lower  degree  of  sharpness,  which  in- 
fluences equally  the  rendition  of  the  tricolor  selection  filter  by  each 
element.  It  is  therefore  obvious  that  it  is  very  important  to  do 
everything  possible  to  prevent  "diffusion"  from  exerting  a  serious 

In  making  sound  films  by  means  of  these  processes,  the  above 
must  be  borne  in  mind  because  the  sensitometry  of  reversed  films 
with  a  solvent  developer  shows  that  industrial  practice  is  attended 
by  unexpected  difficulties.  These  difficulties  are,  moreover,  still 
more  noticeable  with  solvent  ammoniacal  developers. 



[J.  S.  M.  p.  E. 

Very  satisfactory  definition  can  be  attained  by  means  of  lithia 
and  ferrocyanide  combined  with  eikonogen  and  pyrocatechin  B, 
but  the  colors  are  not  as  brilliant  as  they  are  when  ammoniacal  glycine 
is  used,  for  instance.  This  developer  without  ammonia  has  certain 
advantages  from  the  sensitometric  point  of  view,  but  its  "diffusing" 
action,  although  less  than  that  of  many  others,  is  still  too  great  to 
make  it  useful,  especially  when  reproduction  is  concerned  (Bonnerot 
&  Richard,  1926). 

To  return  to  the  sound  film,  it  is  well  known  that  the  printing 

FIG.  1.  Illustrating  the  embossings  in  the  sound  track 
area  of  the  film.  (Film  2  X  natural  size ;  corrugations  90  X 
natural  size.) 

necessitates  certain  precautions;  the  condition  jn  X  JP  =  (K) 
should  be  satisfied  completely.*  As  in  the  Western  Electric  movie- 
tone or  the  Tobis-Klangfilm  processes,  the  average  density  varies 
between  approximately  0.35  and  0.5. 

If  the  sound  be  recorded  on  the  margin  set  aside  for  the  purpose, 
at  the  time  of  printing  the  picture,  and  the  film  be  developed  by 
reversal  according  to  the  known  process,  irregular  results  will  be 

*  7n  =  negative  gamma;  yp  =  positive  gamma;  K  =  constant. 


obtained  because  nearly  always  one  factor  must  be  sacrificed  for  the 
benefit  of  the  other. 

While  in  this  respect  the  variable  width  methods  are  much  more 
flexible,  the  first  development  must  be  continued  to  such  a  point  that 
after  reversal  the  white  spaces  are  perfectly  clear;  it  being  under- 
stood that  the  solvent  reducing  function  has  been  perfectly  balanced. 
These  considerations  lead  to  the  conclusion  that  the  sound  printing  is 
uncertain  under  these  conditions  and  subject  to  all  kinds  of  restric- 
tions. The  following  method  solves  the  problem. 

The  image  is  developed  by  the  usual  solvent  reducing  method,  the 
developer  being  charged  sufficiently  with  bromide.  The  image  is 
reversed  in  permanganate ;  or  better,  in  potassium  dichromate,  owing 
to  its  tanning  action.  The  bleaching  and  clearing  in  sulfite  at  the 
beginning  of  the  washing  should  take  place  in  nonactinic  yellow 
light.  After  this  operation,  the  drying  is  carried  out  in  a  room 
illuminated  with  yellow  light.  The  result  is  a  positive  in  silver  bro- 
mide where  the  margin  has  been  set  aside  for  the  sound  record.'  In 
printing,  it  should  be  remembered  that  the  emulsion  has  lost  its 
speed,  owing  to  the  destruction  of  the  sensitivity  centers  of  the  emul- 
sion grains. 

The  image  is  exposed  again,  giving  it  the  necessary  exposure  for 
obtaining  the  best  result.  We  then  have  a  reexposed  positive  pic- 
ture image,  a  positive  sound  record  in  the  latent  image  state,  and  a 
developer  whose  characteristics  at  an  average  temperature  of  18°C. 
are  known. 

It  is  then  easy  to  obtain  a  sound  positive  in  colors  of  high  quality 
by  development  in  an  ordinary  developer,  the  only  necessary  pre- 
caution being  to  choose  a  developer  that  deposits  reduced  silver  of  a 
color  as  nearly  neutral  as  possible.  After  fixing  and  washing,  the 
final  result  is  obtained. 

By  means  of  the  process  described,  it  is  possible  to  calculate  in 
advance  the  exposure  time  necessary  for  the  sound  and  the  picture 
in  order  that  the  sound  may  satisfy  the  sensitometric  conditions  that 
give  the  best  results. 

When  a  lenticular  sound  film  is  reproduced,  it  is  noticed  that  the 
high  frequencies  are  not  rendered  with  great  fidelity.  The  loss  of 
audibility  is  not  very  great,  but  it  is  sufficient  to  be  noticeable  to  a 
technician.  Hence,  the  sound  margin  should  be  left  smooth  when 
the  film  is  embossed  (Pathe-Kodak  patent) .  A  different  procedure 
can  also  be  adopted  by  making  a  less  pronounced  embossing  on  the 

64  A.  P.  RICHARD 

margin,  the  direction  of  the  lines  being  perpendicular  to  the  slit* 
(Fig.  1). 

The  conditions  for  projection  are  identical  to  those  of  a  film  with  a 
smooth  margin,  and  no  appreciable  difference  between  the  sound 
reproduced  from  a  film  with  a  smooth  margin  and  the  sound  from 
film  with  a  corrugated  margin  can  be  noticed  by  this  method.  More- 
over, the  advantage  of  the  horizontal  corrugation  is  retained  for 
the  picture,  and  additional  frequencies  are  prevented  from  entering 
into  the  sound  band  that  would  otherwise  increase  the  ground  noise. 

1  U.  S.  Pat.  1,460,703,  July  3, 1923;  also  U.  S.  Pat.  1,552,791,  Sept.  8, 1925. 

*  It  should  be  noted  that  the  embossings  in  Fig.  1  have  been  drawn  on  a  greatly 
magnified  scale  compared  with  the  film. 

C.  E.  IVES,  L.  E.  MUEHLER,  AND  J.  I.   CRABTREE** 

Summary. — Fade-outs  have  been  made  for  many  years  by  moving  the  diaphragm 
or  using  a  dissolving  shutter  in  the  camera  during  exposure.  It  is  more  convenient, 
however,  to  make  a  fade  on  either  the  developed  positive  or  negative  film  by  chemical 

A  modified  Belitzski  reducer  formula  of  the  "cutting"  type  is  recommended  for 
negative  fade-outs.  The  film  is  introduced  into  a  tube  or  tank  filled  with  the  solution 
with  a  positive  acceleration  so  that  the  portion  immersed  last  receives  the  least  degree 
of  reduction  and  a  wedge  effect  is  obtained.  Another  method  consists  in  bleaching 
out  the  image  in  either  a  ferricyanide-bromide  or  a  permanganate  bleaching  bath  and 
redeveloping  with  the  same  manipulative  treatment  as  for  reduction.  Positive  fade- 
outs  may  be  made  conveniently  by  tinting  with  a  black  dye  solution. 

A  mechanical  device  is  described  by  means  of  which  the  necessary  acceleration 
may  be  imparted  to  the  film  when  immersing  in  the  various  solutions. 

The  fade-out  (and  fade-in)  has  been  used  extensively  to  cause  a 
pleasingly  gradual  transition  between  successive  scenes  in  a  motion 
picture,  and  is  regarded  in  many  cases  as  a  necessity  for  the  artistic 
presentation  of  the  picture  story.  The  fade-in  and  fade-out  are  essen- 
tially similar  in  nature  although  opposite  in  arrangement,  so  that 
for  convenience  only  the  fade-out  is  referred  to  in  this  paper. 

The  fade-out  can  be  defined  as  a  process  whereby  the  picture  is 
made  to  disappear  from  view  by  a  diminution  of  brightness  and  con- 
trast of  the  picture  toward  the  end  of  a  scene. 

For  many  years  fade-outs  were  made  in  the  camera  by  decreasing 
continuously  the  light  which  reached  the  film  through  the  optical 
system  as  the  end  of  the  scene  was  approached.  Thus,  as  the  fade- 
out  progressed,  the  negative  was  more  and  more  underexposed  until 
at  the  end  of  the  scene  no  image  whatever  was  produced. 

When  a  print  is  made  from  a  negative  which  contains  a  fade-out 
the  printing  exposure  is  not  varied  within  the  scene,  so  that  the  frames 
included  in  the  fade-out  are  progressively  more  dense  and  deficient 

*  Communication  No.  475  from  the  Kodak  Research  Laboratories. 
**  Eastman  Kodak  Co.,  Rochester,  N.  Y. 


66  IVES,  MUEHLER,  AND  CRABTREE  [J.  S.  M.  P.  E. 

in  contrast.  When  such  a  fade-out  is  projected  on  the  screen,  the 
"fading"  is  seen  to  consist  of  the  disappearance  of,  first,  the  shadow 
detail,  second  the  medium  tones,  and  finally  the  highlights. 

As  the  art  of  editing  developed,  it  became  necessary  to  make  the 
fade-out  in  the  developed  negative  after  the  cutting  process  was 
completed.  This  necessitated  either  the  insertion  of  a  duplicate 
negative  in  which  the  fade-out  was  produced  in  the  same  manner  as 
in  the  camera,  or  the  alteration,  by  chemical  treatment,  of  the 
original  negative.  In  the  latter  case  photographic  reducing  solutions 
were  used  to  produce  so-called  "chemical  fades." 

Recently  it  has  been  considered  desirable  to  insert  fades  in  their 
proper  places  in  the  editorially  cut  print  so  that  when  it  is  viewed 
for  final  approval  it  is  complete  in  all  respects.  Any  cutting  or  altera- 
tion is  done  in  the  negative  after  this  print  has  been  approved.  A 
method  of  making  the  required  fades  in  the  positive  has  been  de- 
veloped and  will  be  described  in  this  paper. 


The  first  requisite  of  a  good  fade-out  is  that  it  shall  cause  the 
picture  to  disappear  in  a  gradual  and  continuous  manner.  If  it  is 
abrupt,  or  has  the  appearance  of  being  discontinuous,  it  does  not 
serve  the  function  for  which  it  is  intended.  The  fade-out  must  begin 
at  a  certain  frame  and  go  to  completion  between  this  point  and  the 
end  of  the  scene.  The  average  rate  of  change  of  density  is  deter- 
mined by  this  length  and  the  maximum  density  change  which  must 
be  effected.  The  course  of  the  change  should  be  such  that  when  the 
picture  is  viewed  by  projection  the  average  brightness  appears  to 
diminish  at  a  uniform  rate. 

If  the  change  in  brightness  is  to  appear  uniform,  the  density  of 
each  frame  should  be  related  to  that  of  the  next  by  an  approximately 
constant  difference.  This  is  because,  in  general,  the  eye  appreciates 
as  equal  steps  of  brightness  those  which  are  related  to  each  other  by 
equal  logarithmic  differences.  Since  density  is  a  logarithmic  quan- 
tity, equal  density  steps  in  the  positive  produce  the  desired  logarith- 
mic steps  of  image  brightness  on  the  screen.  In  order  to  produce 
these  equal  density  steps  in  the  positive  the  photographic  reproduc- 
tion characteristic  requires  equal  density  steps  in  the  negative  over  a 
large  part  of  the  fade.  A  fade-out  in  which  the  density  change 
follows  this  course  has  been  found  satisfactory. 

Jan.,  1933  j          MAKING  FADE-OUTS  BY  AFTER  TREATMENT 



In  order  to  make  chemical  fade-outs  in  a  negative  which  are 
similar  in  appearance  to  those  produced  in  the  camera,  a  photo- 
graphic reducing  solution  must  be  employed  which  has  the  property 
of  altering  the  densities  of  the  negative  in  such  a  way  that  it  will 
appear  underexposed  instead  of  underdeveloped.  The  so-called 
cutting  reducers  are  of  this  type,  and  their  action  is  illustrated  by 
the  curves  in  Fig.  1.  In  this  figure,  each  curve  represents  the  densi- 
ties corresponding  to  a  logarithmic  series  of  exposures,  as  is  usual  for 
photographic  characteristic  curves.  Curve  A  shows  the  densities 
before  treatment  with  the  reducer,  and  Curves  B,  C,  and  D  the 
densities  remaining  after  various  degrees  of  reduction.  As  the 







FIG.  1.     Curves  illustrating  the  action  of  cutting  reducers. 

time  of  treatment  is  increased,  the  lower  densities  are  removed 
completely  and  all  densities  are  lowered  by  an  approximately  equal 
amount  which  gives  the  desired  appearance  of  underexposure.  The 
data  from  which  these  curves  were  plotted  were  obtained  by  the  use 
of  a  modified  Belitzski  reducer.1 

In  Fig.  2  are  shown  curves  representing  the  change  of  density  in  a 
highlight  which  took  place  throughout  the  length  of  two  camera 
fades  selected  at  random  from  commercial  productions.  These 
curves  show  considerable  differences,  and  the  departure  from  a  linear 
change  in  density  is  rather  wide.  The  change  in  highlight  density 
with  increasing  distance  from  the  start  of  the  fade-out  is  slow  at  first, 
and  finally  rises  to  an  approximately  constant  rate.  In  view  of  the 
fact  that  a  fade-out  in  which  the  highlight  density  changes  at  a 



[J.  S.  M.  P.  E. 

uniform  rate  throughout  the  fade  has  been  found  to  have  a  pleasing 
and  perfectly  normal  appearance,   it  can  be  concluded  that  the 

FIG.  2.  Curves  illustrating  the  change  of  density  in 
a  highlight  occurring  throughout  the  length  of  two 
camera  fades  selected  at  random  from  commercial 

particular  shape  of  the  curves  in  Fig.  2  indicate  inefficiencies,  and  are 
merely  the  result  of  mechanical  expediency. 


In  Fig.  3  the  progress  of  density  reduction  with  time  of  treatment 
using  the  modified  Belitzski  reducer  is  shown  for  a  highlight  area  in  a 
negative  where  the  original  density  was  0.9.  The  formula  for  this 
reducer  is  given  below. 

Modified  Belitzski  Reducer 

(Formula  R-8) 

Ferric  alum  25 . 0  grams 

Potassium  citrate  75 . 0  grams 

Sodium  sulfite  (anhydrous)  30 . 0  grams 

Citric  acid  20 . 0  grams 

Sodium  thiosulfate  (hypo)  200 . 0  grams 

Water  to  1.0  liter 

Jan.,  1933]          MAKING  FADE-OUTS  BY  AFTER  TREATMENT  69 

The  Belitzski  reducer,  which  is  more  stable,  is  recommended  in 
preference  to  Farmer's  reducer. 

Farmer's  reducer,  as  commonly  used  by  photographers,  consists 
of  a  10  per  cent  solution  of  hypo  in  which  is  dissolved  enough  potas- 
sium ferricyanide  to  cause  the  reduction  to  proceed  at  the  desired 
rate.  Alternatively,  a  two-bath  process  is  sometimes  used  which 
involves  the  use  of  a  potassium  ferricyanide  solution  of  suitable 
strength  for  the  first  bath  and  an  ordinary  fixing  bath  for  the  second.1 

The  two-bath  Farmer's  reducer  can  be  kept  for  long  periods  of 
time,  but  its  use  is  more  complicated  and  control  is  difficult.  When 
the  two-bath  formula  is  used,  the  time  of  treatment  in  the  first 
bath  is  varied  to  give  increasing  degrees  of  reduction  from  one  end 
of  the  fade  to  the  other.  All  parts  of  the  fade  are  then  given  the 
same  time  of  treatment  in  the  second  bath. 

The  three  reducers  mentioned  above  leave  a  faint  stain  image 
which  is  not  ordinarily  objectionable.  When  a  cutting  reducer  is 
required  which  leaves  no  stain  image,  the  iodine-cyanide  reducer  is 
satisfactory,  but  it  has  the  disadvantage  of  being  very  poisonous. 
It  consists  of  a  solution  of  potassium  cyanide  to  which  a  small  quan- 
tity of  iodine  has  been  added. 

Another  method  of  producing  a  fade-out  which  is  free  from  stain 
is  to  bleach  the  entire  length  of  negative  where  the  fade-out  is  to  be 
made,  and  then  to  redevelop  the  image  to  varying  degrees  along  the 
length  to  produce  the  densities  required  in  the  fade. 

Either  of  the  two  bleach  formulas  given  below  is  suitable  for 
converting  the  silver  image  to  one  of  silver  chloride  or  bromide. 

Ferricyanide- Bromide  Bleach 

(Formula  T-lOa) 

Potassium  ferricyanide  20.0  grams 

Potassium  bromide  5 . 0  grams 

Water  to  make  1 . 0  liter 

Permanganate  Bleach 

(Formula  S-6) 
Stock  Solution  A 

Potassium  permanganate  5.3  grams 

Water  to  .     1.0  liter 

Stock  Solution  B 

Sodiumjchloride  75.0  grams 

Sulfuric|acid*  (concentrated)  16.0  cc. 
Water  to  1.0  liter 



For  use,  mix  equal  parts  of  A  and  B  immediately  before  using. 
The  mixed  bath  does  not  keep  long. 

The  silver  chloride  image  can  then  be  redeveloped  to  the  desired 
degree  in  a  developer  such  as  D-16*  diluted  to  one-fourth  strength, 
after  which  the  film  is  fixed  in  an  ordinary  fixing  bath  to  remove  the 
undeveloped  silver  halide. 

Before  redevelopment  is  attempted,  the  bleached  image  should  be 

1  <b 


100  Z.OO  -&OO  400  ^00  0,00  TOO  600  ^00  tOOO 

FIG.  3.     Course  of  reduction  of  motion  picture  panchromatic  type  2  negative 
film  in  modified  Belitzski  reducer. 

exposed  to  strong  daylight,  but  not  sunlight.  The  result  of  the 
bleaching  and  redeveloping  operation  is  equivalent  to  proportional 
reduction,  so  that  the  camera  fade  is  not  simulated  so  closely. 

The  curve  in  Fig.  3  shows  that  the  diminution  of  the  density  of  a 
highlight  with  the  Belitzski  formula  is  not  strictly  proportional  to 
the  time  of  treatment.  The  shape  of  this  curve  is  such,  however,  as 
to  suggest  that  if  that  portion  of  a  negative  where  a  fade-out  is  to  be 

*  Motion  Picture  Film  Developer 
(Formula  D-16) 

Water  (about  125  °F.)  (52  °C.) 


Sodium  sulfite,  desiccated 

(E.  K.  Co.) 
Sodium  carbonate,  desiccated 

(E.  K.  Co.) 
Potassium  bromide 
Citric  acid 

Potassium  metabisulfite 
Cold  water  to  make 



64      ounces 

2.0    liters 

18      grains 

1  .  24  grams 

5      ounces 

158.4    grams 

130      grains 

350      grains 

24.0    grams 

21/2  ounces 

74  .  8    grams 



3 . 44  grams 
2.72  grams 
6 . 0  grams 
4.0  liters 



made  were  led  end  first  at  a  constant  rate  into  the  reducer,  a  very 
acceptable  fade-out  would  be  produced.  This  opinion  is  based 
upon  the  similarity  of  the  curve  produced  in  this  way  and  shown  in 
Fig.  4.  Curve  A  shows  the  densities  remaining  in  the  highlight  of  a 
negative  treated  in  this  manner,  and  Curve  B  shows  the  highlight 



FIG.  4. 

Reduction  of  motion  picture  panchromatic  type 
2  negative  film. 

A,  negative,  time  of  treatment  proportional  to  distance 
from  end  of  fade-out. 

B,  print  from  A  . 

densities  of  a  positive  printed  from  it.  A  print  including  a  fade-out 
made  in  this  way  was  examined  by  projection  and  found  very  satis- 
factory and  entirely  typical. 

Methods  and  apparatus  for  handling  the  film  during  a  treatment  of 
this  kind  are  discussed  later  in  this  paper. 


It  is  assumed  that  a  fade-out  is  to  be  introduced  into  an  editorial 
positive  print  after  it  has  been  developed  and  when  the  editing  is 
complete.  A  convenient  method  of  darkening  the  film  so  as  to 
simulate  a  fade-out  is  to  stain  the  film  with  increasing  quantities  of  a 
neutral  black  dye  as  the  end  of  the  scene  is  approached.  A  satis- 
factory method  of  controlling  the  density  added  in  this  way  is  to 
vary  the  time  of  bathing  in  an  aqueous  solution  of  a  dye  which  has  an 
affinity  for  gelatin. 

No  single  dye  having  the  desired  properties  was  found,  but  a 
combination  of  three  dyes  in  the  formula  given  below  produced  a 

72  IVES,  MUEHLER,  AND  CRABTREE  [J.  S.  M.  P.  E. 

visually  neutral  black  with  a  projector  low-intensity  arc  lamp.  It 
would  be  possible  to  use  these  dyes  in  slightly  modified  proportion 
in  case  the  spectral  distribution  of  the  light  source  used  is  somewhat 
different  from  that  mentioned.  The  formula  can  be  considered 
merely  as  a  guide  to  the  proper  proportions,  because  various  samples 
of  the  same  dyestuff  are  often  found  to  differ  in  purity. 

Visually  Neutral  Dye  Bath 

Acid  anthracene  brown  B*  8.7  grams 

Toluidine  blue  *  *  8.7  grams 

Naphthol  green**  2. 6  grams 

Water  to  make  1 . 0  liter 

In  deciding  upon  the  density  to  be  added  by  dyeing,  preliminary 
tests  were  made  which  showed  that  a  maximum  density  of  about  4.0 
should  be  reached  in  order  to  obliterate  the  image  entirely.  This 
density  seems  rather  high,  but  is  necessitated  by  the  fact  that  the 
contrast  is  not  degraded  by  the  addition  of  a  uniform  density  over 
the  picture.  It  is  necessary,  therefore,  to  increase  the  superimposed 
density  to  a  point  where  even  the  brightest  part  of  the  image  is 
covered  effectively.  This  condition  is  usually  attained  when  the 
added  density  is  4.0  because  of  several  factors.  Among  these,  the 
following  are  important: 

(a)  Visual  contrast  perception  is  greatly  reduced  at  a  screen  brightness  level 
equal  to  one  ten-thousandth  of  the  ordinary  level. 

(b)  The  adaptation  level  of  the  eye  in  an  ordinary  auditorium  or  theater  is 
usually  at  a  level  which  is  much  higher  than  that  which  would  give  the  best 
contrast  perception  when  the  fade-out  is  in  progress. 

(c)  The  stray  light  falling  on  the  screen  is  usually  enough  to  obliterate  the 
image  beyond  a  brightness  level  reached  during  the  fade. 

From  the  considerations  cited  previously,  it  was  concluded  that  a 
constant  change  in  density  with  distance  along  the  fade  would  be 
suitable.  Tests  of  positive  fades  made  in  this  way  proved  satis- 
factory on  projection. 

It  was  found  that  the  density  produced  by  the  dye  formula  given 
above  was  proportional  approximately  to  an  exponential  of  the  time 
of  bathing,  as  shown  by  the  curve  in  Fig.  5.  In  order  to  obtain, 

*  Grasselli  Chemical  Co.,  Inc.,  Empire  State  Bldg.,  New  York,  N.  Y. 
**  Hoechst  (marketed  by  General  Dyestuff s  Corp.,  233  Fifth  Avenue,  New 
York,  N.  Y.). 



on  each  frame,  a  density  which  is  directly  proportional  to  the  dis- 
tance from  the  end  of  the  fade  it  was  necessary  to  vary  the  time  of 
treatment  throughout  the  length  of  the  fade  in  a  manner  which  is 
functionally  related  to  the  exponential  rate  of  growth  of  density  with 




IOO  ZOO  "iOO  4OO  5OO  fcOO  1OO 

FIG.  5.     Dye  tinting  of  motion  picture  positive  film. 

time  of  treatment.  A  fade-out  of  this  type,  the  curve  of  which  is 
shown  at  A  in  Fig.  6,  was  made  by  timing  the  dye  treatment  accord- 
ing to  the  indications  of  the  curve  in  Fig.  5,  to  give  a  constant  rate  of 
increase  in  density  along  the  length. 

Curve  B  in  Fig.  6  shows  the  densities  produced  by  leading  the  film 
at  a  constant  rate  into  the  dye  solution,  a  procedure  which,  as  might 
be  expected,  gives  very  poor  results. 


FIG.  6. 

10,  ZA  VZ.  40  AB 

Dye  tinting  of  motion  picture  positive  film. 


A,  added  density  proportional  to  distance  of  fade-out;  B,  time  of 
treatment  proportional  to  distance  from  end  of  fade-out;  C,  timing 
by  simple  crank  and  connecting  rod  mechanism. 

Curve  C  in  Fig.  6  shows  the  densities  which  resulted  from  times  of 
treatment  which  could  be  given  by  a  simple  crank  and  connecting  rod 
mechanism.  This  fade-out  was  found  quite  satisfactory. 

Of  the  numerous  ways  of  causing  a  varying  degree  of  chemical 

74  IVES,  MUEHLER,  AND  CRABTREE  [J.  S.  M.  P.  E. 

treatment  from  one  end  of  the  fade  to  the  other,  the  simplest  is  to  vary 
the  time  of  treatment. 


In  the  case  of  the  application  of  a  dye  solution  to  the  film,  the 
treatment  can  be  carried  out  according  to  one  of  the  methods  for 
which  instructions  are  given  below. 

(1)  With  the  film  strip  lying  emulsion  side  up  on  a  flat  surface,  rub  the  sur- 
face lengthwise  with  a  wad  of  cotton  soaked  with  the  dye  solution.    Start  each 
stroke  at  the  end  which  is  to  receive  the  lesser  time  of  treatment.    As  each  frame 
in  succession  receives  its  full  time  of  treatment,  blot  it  off  and  guard  it  from 
further  contact  with  the  cotton  wad.    As  treatment  is  discontinued  on  one  frame 
after  another,  the  swabbing  stroke  is  thereby  shortened  more  and  more.    When 
the  treatment  of  the  whole  strip  is  completed  it  should  be  free  from  spots  of  liquid 
and  should  not  be  washed  but  is  ready  for  use  when  dried. 

(2)  If  a  large  number  of  fades  are  to  be  made,  it  is  preferable  to  treat  several 
strips  at  a  time  by  lowering  them  at  a  predetermined  rate  into  a  tank  or  tray 
containing  the  dye  solution.    That  end  of  the  strip  which  is  to  be  bathed  for  the 
shortest  time  is  immersed  into  the  bath  last.    When  the  treatment  is  completed, 
draw  the  strips  quickly  from  the  bath,  passing  them  through  a  squeegee  to  remove 
excess  liquid  from  the  surface.    The  fade  is  ready  for  use  as  soon  as  it  is  dry. 

The  equipment  required  for  this  operation  depends  upon  the 
method  of  timing,  and  may  vary  from  a  wooden  rod  with  hooks  to  which 
the  various  strips  are  attached,  to  a  completely  automatic  machine  by 
which  the  treatment  is  timed  and  the  film  withdrawn  and  squeegeed. 
The  elaboration  of  the  equipment  will  depend  on  the  quantity  of 
work  to  be  done,  but  perfectly  satisfactory  results  can  be  obtained 
with  the  simplest  equipment.  Methods  of  automatically  controlling 
the  time  of  treatment  are  discussed  below. 


The  mechanical  handling  of  the  negative  during  treatment  is 
essentially  similar  to  that  of  the  positive,  but  certain  limitations  are 
imposed  by  the  nature  of  the  processes.  Both  reducing  solutions 
and  developers  which  are  used  in  producing  negative  fade-outs  act 
upon  the  image  at  a  rate  which  is  slower  than  the  rate  of  diffusion 
from  the  solution  into  the  gelatin.  The  consequence  of  this  is  that 
when  the  film  is  removed  from  the  bath  it  contains  a  considerable 
quantity  of  unused  solution  which  continues  to  work  unless  prevented 
by  prompt  action.  The  operation  must  be  planned,  therefore,  in 
such  a  way  that  the  treatment  of  all  portions  of  the  fade  is  com- 
pleted simultaneously,  and  provision  must  be  made  for  quick  re- 

Jan.,  1933]          MAKING  FADE-OUTS  BY  AFTER  TREATMENT  75 

moval  to  the  next  bath  or  the  wash,  as  the  case  may  be.  Usually 
the  action  continues  to  a  slight  extent  in  the  subsequent  bathing  or 
washing,  but  this  can  be  minimized  by  adequate  agitation  of  the  film 
in  the  bath.  At  any  rate,  the  further  action  can  be  made  definite  and 
uniform  by  proper  handling,  and  allowance  can  be  made  for  it  in  the 
determination  of  the  time  of  treatment. 

The  following  procedure  assures  a  satisfactory  fade-out  when  the 
times  of  treatment  have  been  determined  properly  for  the  existing 

(1)  The  Belitzski,  one-bath  Farmer,  or  Iodine-Cyanide  reducing 
solution  should  be  placed  in  a  tank  or  tray  large  enough  to  accommo- 
date the  full  length  of  the  fade-out.     Lead  the  strip  into  the  bath  at  a 
rate  which  will  give  to  each  frame  the  time  of  treatment  found  neces- 
sary in  previous  trials.     Allow  the  end  which  is  to  receive  the  least 
time  of  treatment  to  enter  the  bath  last.     Keep  the  liquid  moving 
during  use  to  assure  uniformity  of  treatment.     This  is  especially 
advisable  in  a  shallow  tray  where  natural  circulation  is  very  little. 

When  the  treatment  is  complete,  draw  the  strip  out  quickly,  prefer- 
ably through  a  squeegee,  and  place  it  in  running  water.  Agitate 
thoroughly  during  the  first  minute  of  the  wash  to  remove  the  reducer 

(2)  When  the  two-bath  Farmer  reducer  is  used,  the  treatment 
in  the  first  bath  is  carried  out  as  described  under  method  No.  1 
above.     When  the  film  is  removed  from  this  solution,  it  is  placed 
in  the  second  bath  where  it  should  be  agitated  for  1  minute  and  then 
allowed  to  remain  for  about  10  minutes. 

(3)  The  following  directions  apply  for  the  bleach  and  redevelop 
process:    Bathe  the  whole  fade-out  in  the  bleaching  solution  for  a 
time  somewhat  longer  than  that  required  to  show  the  pale  yellowish 
white  color  through  the  film  support.     When  bleaching  is  complete, 
remove  the  film  and  wash  it.     (If  the  permanganate  bleach  has  been 
used,  the  dark  brown  stain  should  be  removed,  before  washing,  by  a 
short  treatment  with  a  1  per  cent  solution  of  sodium  bisulfite.)     When 
washing  is  complete,  the  fade-out  is  produced  by  lowering  the  film  end 
first  into  an  ordinary  developing  solution  which  may  be  diluted  for 
convenience  in  timing. 

The  end  of  the  fade-out  which  is  to  have  the  greatest  density  should 
enter  the  developer  first.  When  all  portions  of  the  fade  have  received 
the  proper  times  of  development  as  determined  in  previous  trials, 
the  fade  is  removed  quickly  to  an  acid  fixing  bath,  where  it  is  agitated 

76  IVES,  MUEHLER,  AND  CRABTREE  [J.  S.  M.  P.  E. 

for  about  1  minute  and  then  allowed  to  remain  for  10  minutes.  Fixa- 
tion is  followed  by  washing  and  drying,  after  which  the  fade-out  is 
ready  to  be  spliced  to  the  negative. 

It  is  advisable,  before  any  of  the  above  operations  on  negatives 
are  undertaken,  to  harden  the  gelatin  by  treatment  for  five  minutes 
in  the  following  hardening  solution. 

Hardening  Solution 

(Formula  SH-2) 

Formalin  (40%  solution)  5.0  cc. 

Sodium  carbonate  (anhydrous)  5 . 0  grams 

Water  to  1.0  liter 

If  the  negative  has  not  been  properly  hardened,  reticulation  and 
frilling  of  the  gelatin  are  liable  to  occur  in  the  after  processes. 


Although  it  would  appear  that  the  motion  of  the  treated  strip  of 
film  should  be  stepwise  so  that  all  portions  of  a  single  frame  receive 
the  same  treatment,  this  is  not  necessary.  In  a  fade  of  the  usual 
length,  the  change  is  so  gradual  that  no  variation  in  density  from 
top  to  bottom  of  the  frame  can  be  detected  if  the  fade  is  produced  by 
leading  the  film  into  the  treating  solution  by  a  continuous,  instead  of 
stepwise,  motion.  This  makes  possible  a  wider  choice  of  methods  of 

If  the  handling  is  to  be  entirely  manual,  then  the  stepwise  method 
is  probably  the  best  choice,  because  of  the  difficulty  of  estimating 
the  velocity  in  a  continuous  motion.  It  is  recommended  to  adjust 
the  concentration  of  the  solution  so  that  the  process  is  complete  in 
about  10  minutes. 

If  the  time  of  treatment  is  to  vary  directly  as  the  length  of  film 
traversed,  the  film  can  be  led  into  the  bath  either  one  frame  at  a 
time  at  equal  time  intervals,  or  continuously  by  the  use  of  any  one 
of  the  common  mechanical  arrangements  for  producing  motion  at  a 
constant  rate.  The  use  of  mechanical  timing  means  is  very  desir- 
able, even  though  a  large  part  of  the  process  is  to  be  carried  on 

If  the  time  of  treatment  is  not  required  to  increase  directly  as  the 
length  of  film,  then  a  more  complicated  timing  means  must  be 
chosen.  As  shown  in  Fig.  5,  for  the  dye  treatment  the  relationship 
between  time  of  treatment  and  length  traversed  is  exponential, 
a  relationship  which  is  not  attained  precisely  in  a  simple  mechanical 

Jan.,  1933]          MAKING  FADE-OUTS  BY  AFTER  TREATMENT 


device.  If  the  motion  is  controlled  by  the  use  of  a  cam  of  special 
shape  the  apparatus  is  somewhat  expensive  and  usually  awkward 
and  difficult  to  alter  for  varying  the  treatment. 

A  device  described  in  a  previous  communication2  may  be  used 
for  the  purpose  because  it  can  be  adapted  very  easily  to  control  the 
motion  in  any  manner  desired.  This  device  is  illustrated  schemati- 
cally in  Fig.  7  with  some  of  the  other  equipment  which  might  be  used 
for  handling  the  film.  The  timing  element  proper  consists  of  a  tape 
moved  at  a  constant  rate  under  a  set  of  small  levers.  Perforations 

FIG.  7. 

Schematic  drawing  of  machine  for  making  fades  with 
tape  for  program  timing. 

made  in  the  tape  at  the  necessary  points  move  the  levers,  making 
electrical  contacts  by  which  the  film  advancement  ratchet  can  be 
moved,  motors  started,  stopped,  reversed,  etc. 

There  are  other  devices  commercially  available  for  timing  a  pre- 
determined sequence  of  events,  such  as  the  blowing  of  time  whistles, 
ringing  bells,  etc.,  which  might  be  adapted  to  this  purpose.  As  men- 
tioned above,  there  is  always  the  possibility  that  an  approximation 
of  the  motion  required  which  is  much  more  readily  attained  will  be 
equally  satisfactory  in  practice. 


In  the  construction  of  apparatus  for  the  treatments  described  in 
this  paper  it  is  necessary  to  take  into  account  the  corrosive  nature 
of  the  solutions  when  deciding  upon  the  material  to  be  used  in  con- 
tact with  the  bath  or  the  wet  film.3 


1  CRABTREE,  J.  I.,  AND  MUEHLEP,  L.  E.:     "Reducing  and  Intensifying  Solu- 
tions for  Motion  Picture  Film,"  /.  Soc.  Mot.  Pict.  Eng.,  XVII   (Dec.,  1931), 
No.  6,  p.  1001. 

2  JONES,  L.  A.:     "A  New  Non-Intermittent  Sensitometer,"  /.  Frank.  Inst., 
189  (1920),  No.  3,  p.  303. 

3  CRABTREE,  J.  I.,  MATTHEWS,  G.  E.,  AND  Ross,  J.  F.:     "Materials  for  the 
Construction  of  Motion  Picture  Processing  Apparatus,"  /.  Soc.  Mot.  Pict.  Eng.t 
XVI  (March,  1931),  No.  3,  p.  330. 



Summary. — The  paper  opens  with  a  few  remarks  on  the  relation  between  the 
musician  and  the  engineer,  and  refers  particularly  to  certain  inadequacies  in  the 
recording  and  reproduction  of  music.  The  improper  acoustical  construction  of  sets 
and  the  inappropriate  placing  of  artists  and  accompanists  are  alluded  to.  The 
difficulty  of.  satisfactorily  recording  background  music  is  briefly  discussed,  and  a 
suggestion  is  made  for  overcoming  the  masking  of  dialog  by  background  music. 
Further  remarks  are  made  on  the  size  of  sets  and  various  points  of  technic  in  recording 
and  duping. 

In  discussing  the  practical  problems  that  confront  us  in  the  every- 
day experiences  on  the  stages  of  the  studio,  let  us  first  disregard  en- 
tirely the  attitude  of  the  industry  as  a  whole — disheartening,  to  say 
the  least — toward  all  endeavors  of  pioneering  into  new  realms  of 
imagination  and  fantasy.  I  believe  that  you  will  agree  that  unless 
startling  improvements  are  made  in  the  recording  and  reproducing 
of  sound  pictures,  even  beyond  what  has  been  done  up  to  now, 
the  industry  may  see  a  further  divorcement  between  the  theater  and 
the  audience  than  it  has  already  seen. 

The  musician  feels  a  common  bond  with  the  engineer,  in  respect 
to  the  reproduction  of  sound,  first,  because  as  an  artist  he  depends 
so  much  upon  the  indulgence  of  the  engineer  and,  second,  because 
he  is  keenly  aware  of  the  well-nigh  overwhelming  technical  problems. 
I  have  found  the  great  majority  of  "mixers"  I  have  worked  with  to 
be  most  genial  and  sympathetic;  and  have  sometimes  been  amazed 
at  the  appreciation  shown  by  these  men,  not  only  of  sound  as  spoken 
of  in  decibels,  but  as  regards  a  fine  feeling  for  music  in  all  its  com- 
ponents of  inspirational  value — the  balance  of  orchestration  and  the 
most  illusive  emotional  factors  that  comprise  an  artistic  performance. 

Many  present-day  troubles  result  from  two  factors:  (1)  a  lack  of 
understanding  of  the  other  fellow's  problem,  and  (2)  the  yet  un- 

*  Presented  at  a  meeting  of  the  New  York  Section,  Oct.  19,  1932. 
**  Warner  Bros.  Pictures,  Inc.,  Brooklyn,  N.  Y 


80  D.  MENDOZA  [J.  s.  M.  P.  E. 

conscious  and  unexpressed  opinions  of  our  audiences  at  large  as  to 
their  reactions  to  "sound." 

I  feel  that  our  stages  are  sorely  lacking  as  to  physical  proportions 
and  proper  material  for  the  effective  recording  of  music.  The  stack- 
ing of  deadening  and  in  many  instances  reflective  sets  is  most  harm- 
ful. Our  orchestras  are  shunted  into  all  manner  of  positions  and 
locations  so  as  to  be  out  of  the  way,  as  it  were,  of  camera  lines,  and 
to  be  "conveniently"  placed.  Soloists  are  usually  placed  at  absurd 
distances  from  the  accompanists.  Under  such  conditions,  balancing 
for  the  mixer  becomes  merely  a  catch-as-catch-can  affair.  Even  on 
the  coast,  with  the  stupendous  stages  found  on  all  the  lots,  the  sets 
are  generally  built  with  a  thought  only  for  the  cameras. 

Another  factor  that  results  from  a  lack  of  cooperation  and  under- 
standing between  departments  refers  to  the  matter  of  orchestration. 
The  mixer  generally  hears  the  first  performance  of  the  musical  com- 
positions in  his  monitor  room,  and  is  not  generally  aware  of  some 
of  the  niceties  of  the  orchestration,  which  should  be  determined  by 
the  playback. 

A  few  weeks  ago  we  had  occasion  to  place  the  orchestra  on  a  plat- 
form about  four  feet  high,  which  happened  to  be  built  for  use  as  a 
bridge  in  a  scene  to  be  shot  the  next  day.  By  placing  the  orchestra 
on  this  platform,  with  its  good  air  space  beneath  and  all  the  "life" 
resulting  from  the  platform,  we  were  afforded  one  of  the  most  satis- 
factory recordings  obtained  in  a  long  time.  This  is  a  point  upon 
which  I  put  a  great  deal  of  stress,  for  orchestras  are  expensive  and 
unless  we  obtain  satisfactory  results  the  efforts  and  expenditure 
involved  will  have  been  greatly  vitiated. 

Now  we  come  to  one  of  the  most  deplorable  facts  in  connection 
with  music  in  motion  pictures,  namely,  "background"  music.  Of 
course,  where  a  picture  is  silent  as  far  as  dialog  is  concerned,  the 
music  has  a  pretty  good  chance  to  come  through  satisfactorily,  but 
when  the  characters  on  the  screen  speak,  the  music  is  wholly  ineffec- 
tive and  in  any  case  unsatisfactory.  If  we  were  to  have  an  orchestra 
in  the  theater  to  supply  mood  and  background  music  for  pictures, 
the  music  should  emanate  from  a  source  entirely  different  from  that 
from  which  the  dialog  would  come.  It  would  be  easy  to  "balance" 
the  music  and  dialog,  and  lose  none  of  the  effectiveness  of  either  one 
or  the  other.  Would  it  not  be  possible  to  develop  a  double  sound 
track,  one  on  each  side  of  the  film,  and  place  the  projecting  horns  at 
different  places  in  the  proscenium  of  the  theater?  One  track  could 

Jan.,  1933]          RECORDING  AND  REPRODUCTION  OF  MUSIC  81 

carry  the  music  and  the  other  the  dialog;  the  two  tracks  could  be 
reproduced  on  different  systems  and  each  could  be  operated  inde- 
pendently of  the  other  and  reproduced  from  different  points  of  the 
proscenium.  This  thought  may  be  very  impracticable,  but  as  I  should 
like  very  much  to  see  something  done  in  this  connection,  as  I  feel  sure 
that  the  proper  musical  accompaniment  of  pictures  would  greatly 
assist  in  improving  the  reaction  of  the  audience.  I  believe  that  you 
will  all  agree  with  me  that  up  to  the  present  a  really  effective  back- 
ground musical  score  has  not  been  accomplished. 

Also,  when  a  dramatic  scene  is  on  the  screen  and  silence  prevails 
for  a  few  minutes,  the  issuance  of  music  from  the  same  source  whence 
comes  the  dialog  seems  unnatural.  The  producers  always  try  to 
create  an  apologia  for  the  music,  and  either  place  a  radio  or  a  phono- 
graph in  the  scene.  The  audiences  are  becoming  aware  of  this 
clumsy  form  of  excuse,  and  are  making  many  humorous  comments 
about  it. 

I  mentioned  before  my  sentiments  regarding  the  size  of  our  stages. 
In  the  case  of  close-up  recordings  of  solo  instruments,  they  do  not 
apply ;  but  when  an  orchestra  of  symphonic  proportions  is  employed 
we  have  found  it  well-nigh  impossible  to  allow  the  men  to  play  in  full 
tone  fortissimo,  as  they  would  in  a  concert  hall.  On  the  radio  we 
hear  reproductions  of  symphony  orchestras  with  a  great  deal  of 
satisfaction  as  regards  results.  Why  can  we  not  achieve  as  good 
results  on  our  screen?  The  only  remedy  that  I  can  think  of  is  to 
utilize  recording  space  so  that  it  permits  placing  the  microphones 
at  a  distance  that  would  allow  a  natural  performance  and  yet  provide 
good  acoustical  results  when  reproduced.  The  new  developments 
recently  made  in  extending  the  range  of  reproduced  frequencies 
could  then  be  fully  appreciated. 

You  have  no  idea  of  how  great  is  the  difference  in  the  feelings  of 
musicians  when  they  are  allowed  to  play  on  a  stage  that  is  "alive" 
and  spacious.  Everything  seems  to  be  pleasant  and  simple.  The 
effect  is  purely  psychological,  but  it  is  one  of  the  main  factors  in  our 
particular  work.  The  conditions  of  recording  have  a  tremendous 
effect  upon  the  performer.  So  far,  men  like  Respighi  and  Ravel  have 
not  been  enticed  into  the  motion  picture  field,  and  I  think  that  this 
is  mainly  because  the  conditions  existing  in  recording  studios  are  in 
no  way  as  conducive  as  they  should  be  to  a  high  standard  of  artistic 

I  remember  a  story  that  was  told  to  me  about  Fritz  Kreisler.     The 

82  D.  MENDOZA  [j.  s.  M.  p.  E. 

occasion  was  a  recording  date  for  the  Victor  Company.  Kreisler 
took  out  his  violin,  stepped  before  the  horn  (this  was  in  the  "good" 
old  recording  days),  and  noticed  that  he  was  standing  on  a  rug. 
He  asked  the  reason  for  the  rug  and  was  informed  that  it  was  neces- 
sary for  acoustical  reasons.  Thereupon  Mr.  Kreisler  expressed 
himself  as  being  unable  to  play  unless  he  stood  on  the  bare  floor. 
This  story  may  sound  far-fetched  and  may  be  foolish  as  far  as  net 
results  are  concerned,  but  as  the  performer  was  Mr.  Kreisler  and 
none  else,  the  rug  was  removed. 

Now  imagine  our  trying  to  perform  on  crowded  stages  filled  with 
all  sorts  of  deadening  materials,  such  as  flats,  that  set  up  all  kinds  of 
reverberations,  and  situated  so  that  we  have  no  idea  of  what  the  net 
balance  will  be.  Yet  we  struggle  on  in  the  hope  that  some  day  our 
work  will  be  facilitated  to  a  point  that  will  spur  our  enthusiasm  and 

I  do  not  believe  that  any  method  of  equalization  for  duping 
purposes  is  advisable,  as  I  have  found  that  if  the  original  sound  track 
does  not  possess  all  the  qualities  desired,  any  attempt  to  equalize 
for  the  purpose  of  building  up  highs  or  lows  generally  introduces 
some  kind  of  distortion. 

I  am  aware  that  there  are  various  new  improvements  being  utilized 
and  experimented  on  that  I  understand  give  results  far  superior  to 
what  we  are  producing  at  present.  I  sincerely  hope  that  the  producers 
will  be  made  to  realize  the  advisability  of  adopting  these  improve- 
ments. The  engineers  must  sell  these  ideas  to  these  producers, 
especially  in  the  matter  of  theater  equipment;  for,  as  is  well  known, 
many  of  our  efforts  are  vitiated  in  the  net  results  heard  in  the  neigh- 
borhood theaters  and,  in  many  cases,  I  am  sorry  to  say,  in  the  so-called 
de  luxe  motion  picture  houses. 

Of  course,  few  theaters  have  been  built  particularly  for  exhibiting 
sound  pictures.  We  hear  our  product  in  our  small  projection  rooms, 
and  are  very  often  enthusiastic  over  the  results.  Later  we  hear  it 
in  one  of  the  Broadway  theaters,  and  the  difference  is  unbelievably 
disappointing.  The  music  sounds  thin,  without  the  body  of  sound 
that  I  know  was  contained  in  the  original  recording.  High  tones  are 
lost,  low  tones  are  lost — "fuzz,"  "edge,"  sprocket  hole  modulation 
are  produced.  The  problems  in  this  connection  are  too  numerous 
to  relate  and  I  am  in  absolute  sympathy  with  the  engineers'  efforts. 
But  when  I  hear  my  oboe,  clarinet,  violin,  or  trumpet  sound  like  a 
Chinese  cat,  I  resent  it !  I  must  resent  it !  Poor  balance  can  be 

Jan.,  1933]          RECORDING  AND  REPRODUCTION  OF  MUSIC  83 

corrected  even  in  mixing,  poor  performance  in  rehearsal — and 
"fuzz"  and  "edge"  must  be  eliminated. 

A  word  for  duping.  This  is  one  of  the  phases  of  our  business  that 
I  think  is  still  in  its  most  elementary  state.  An  evil  in  itself  and 
unavoidable  from  a  practical  and  economic  point  of  view — but  the 
relation  between  the  dynamics  of  music  back  of  dialog  plus  effects  is  a 
matter  of  showmanship  in  its  most  elementary  phase.  The  dupers 
and  mixers  are  endeavoring  to  be  showmen  in  this  sense,  and  in  many 
instances  they  are.  The  mere  audibility  of  any  sound,  either  music 
or  effect,  is  not  enough.  That  the  importance  of  the  sound  lies  in 
the  frame  of  the  drama  or  the  comedy  is  the  factor  to  bear  in  mind. 
A  moment  of  drama  must  be  recognized  as  such,  and  soft  and  subtle 
treatment  is  necessary. 

Now  I  do  not  believe  that  all  these  shortcomings  are  due  to  in- 
adequate equipment.  I  attribute  a  great  deal  of  it  to  faulty  and 
inadequate  acoustics.  From  the  standpoint  of  dialog,  the  motion 
picture  is  well  exhibited;  but  from  the  standpoint  of  sound,  I  am  sorry 
to  reiterate  that  most  of  the  comments  of  those  who  pay  attention 
to  this  part  of  the  entertainment  are  always  most  disappointing. 

In  conclusion,  I  wish  to  state  that  complete  cooperation  and  very 
close  association  must  exist  between  the  music  department  and 
the  recording  department.  A  complete  understanding  of  each 
other's  problems  and  the  exchange  of  ideas  and  an  honest  criticism 
of  each  other's  work  must  be  the  rule.  Temperament  will  always 
be  present,  but  if  honesty  exist  fundamentally,  good  results  will 


The  following  correction  should  be  made  in  the  paper,  Standards  and  Require- 
ments of  Projection  for  Visual  Education,  by  Chauncey  L.  Greene,  beginning  on 
page  424  of  the  November,  1932,  issue  of  the  JOURNAL: 

On  page  432,  sixth  line  from  the  bottom,  the  phrase  "this  class  of  screen" 
should  read  "the  translucent  type  of  screen." 


At  recent  meetings  of  the  photographic  section  of  the  Technicians  Branch  of  the 
Academy  of  Motion  Picture  Arts  and  Sciences,  and  of  the  Chicago  Section  of  the 
S.  M.  P.  E.,  several  pieces  of  new  equipment  were  exhibited  and  discussed.  The 
description  of  a  few  of  the  devices  follows.  Illustrations  were  supplied  by  Mr.  J.  G. 
Frayne,  Chairman  of  the  S.  M.  P.  E.  Progress  Committee  and  Mr.  C.  E.  Phillimore 
of  the  S.  M.  P.  E.  Chicago  Section. 

Bell  &  Howell  Rotambulator  (Fig.  1). — With  this  new  type  of  sup- 
port, the  camera  may  be  moved  vertically  from  a  point  2  feet  above 
the  floor  to  nearly  8  feet.  Present  models  utilize  a  worm  drive  for 
this  movement  but  future  models  may  be  equipped  with  a  hydraulic 

Courtesy  of  Bell  &•  Howell  Co. 

FIG.  1.     Rotambulator. 

hoist.  The  usual  pan  and  tilt,  and  horizontal  movements  are 
available.  The  panoramic  movement  is  effected  by  hydraulic 
means,  and  is  controlled  by  pedals  operated  by  the  cameraman,  who 
sits  on  a  seat  arranged  to  revolve  with  the  camera.  The  device  is 



Follow- Focus 
Device  for 
Actuating  Finder 

'Lupe*  Light  Bracket 

Llftlnc  Handle  (4) 

Courtesy  of  Paramount  Publix  Corp. 

FIG.  2.     Sound  blimp. 

Courtesy  of  Paramount  Publix  Corp. 

FIG.  3.     Camera  crane 

86  NEW  APPARATUS  [J.  S.  M.  p.  E. 

mounted  on  a  heavy  frame  equipped  with  three  small  wide  wheels 
having  rubber  tires.  A  hand  bar  is  provided  for  moving  the  rotambu- 
lator  and  the  cinematographer. 

Paramount  Sound  BUmp  (Fig.  2) . — The  illustration  is  self-explana- 
tory. Note  that  the  camera  and  tripod  may  be  lifted  quickly  and 
easily  by  the  rolling  tripod  for  moving  from  one  setting  to  another. 

Courtesy  of  Peko,  Inc. 

FIG.  4.     Projector. 

Paramount  Camera  Crane  (Fig.  3). — This  crane  is  so  designed  that 
it  may  be  passed  through  a  24-inch  doorway.  It  is  much  more 
flexible  and  lighter  in  weight  than  many  of  the  earlier  cranes  used  for 
motion  picture  camera  work. 

Peko  Projector  (Figs.  4  and  5). — The  frame  consists  of  a  white-brass 
casting  about  which  the  entire  mechanism  is  constructed.  The 
gear  train  comprises  four  spur  gears  and  two  metal  gears.  All 
bearings  are  lubricated  from  tubes  leading  to  the  top  of  the  machine. 
The  intermittent  movement  consists  of  a  conventional  cam  and  a 
double  claw  straddling  the  perforations.  A  two-blade  90-degree 
shutter  is  employed,  the  picture  being  projected  at  the  rate  of  20 
frames  per  second.  The  reflector  is  made  of  chromium-plated  brass. 

Jan.,  1933] 



The  base  of  the  projector  houses  a  transformer  or,  in  the  case  of 
d-c.  supply,  a  resistor.  The  projectors  are  designed  to  be  operated 
by  alternating  or  direct  current.  The  driving  belt  is  crossed  to  per- 
mit reversing  the  machine  or  rewinding  the  film. 

The  film  passes  through  the  projector  without  being  twisted  and 
ball  bearings  are  used  throughout.  The  reels  will  accommodate  400 
feet  of  film. 

One  model  is  provided  with  a  rheostatic  speed  control  and  a  special 
switch  by  means  of  which  a  resistor  is  introduced  into  the  lamp  cir- 
cuit when  the  motor  is  at  rest,  thereby  reducing  the  illumination  and 
heat  sufficiently  to  permit  showing  still  pictures.  Forced  ventilation 
is  also  provided. 

Courtesy  of  Peko,  Inc. 

FIG.  5.     Projector  mounted  in  carrying  case;     right,   for  direct  projection 
through  front  of  case;  left,  for  industrial  use  with  daylight  screen. 


Einfuehrung  in  die  Tonphotographie.  (Introduction  to  Sound-Photography.) 
JOHN  EGGERT  AND  RICHARD  SCHMIDT.  S.  Hirzel,  Leipzig,  1932,  137  pp. 

This  introduction  gives  a  thorough  resume  of  methods  of  recording  sound 
photographically.  After  briefly  describing  the  elementary  physics  of  sound 
recording,  it  deals  with  the  various  electrooptical  phenomena  and  their  application 
to  modern  methods  of  recording  sound. 

The  greater  portion  of  the  book  is  devoted  to  the  fundamental  principles  of 
photographic  recording.  In  some  ways  very  elementary,  these  chapters  furnish 
a  rather  complete  analysis  of  most  of  the  known  photographic  effects  on  the 
sound  record  and  discuss  the  influence  of  these  effects  on  the  final  results:  the 
reproduced  sound.  Following  a  treatise  on  sensitometry  is  a  chapter  on  the 
fundamental  requirements  for  recording  and  reproducing  sound  without  distor- 
tion. Both  the  variable  area  and  the  variable  density  systems  of  recording  are 
discussed,  as  well  as  the  noiseless  recording  systems. 

The  latter  part  of  the  book  presents  results  obtained  with  Agfa  Film  TF3  and 
TF4;  films  especially  made  and  adapted  for  recording  sound,  which  are  exten- 
sively used  in  Europe.  A  proposal  for  standardization  and  citations  of  German, 
English,  and  American  literature  conclude  the  volume. 

Many  graphical  charts  and  drawings,  which  can  be  easily  understood  with  but 
little  knowledge  of  mathematics,  illustrate  the  formulas. 

This  book  should  be  of  great  value  to  all  those  interested  in  the  problems  of 
recording  sound.  W.  SCHMIDT 




A.  N.  GOLDSMITH,  Radio  Corporation  of  America,  New  York,  N.  Y. 

J.  I.  CRABTREE,  Eastman  Kodak  Company,  Rochester.  N.  Y. 


E.  I.  SPONABLE,  Fox  Film  Corp.,  New  York.  N.  Y. 
W.  C.  KUNZMANN,  National  Carbon  Co.,  Cleveland,  Ohio. 

J.  H.  KURLANDER,  Westinghousc  Lamp  Co.,  Bloomfield,  N.  J. 

H.  T.  COWLING,  Rochester,  N.  Y. 

Board  of  Governors 

H.  T.  COWLING,   311  Alexander  St.,  Rochester,  N.  Y. 

J.  I.  CRABTREE,  Research  Laboratories,  Eastman  Kodak  Co.,  Rochester,  N.  Y. 

P.  H.  EVANS,  Warner  Bros.  Pictures,  Inc.,  1277  E.  14th  St.,  Brooklyn.  N.  Y. 

R.  E.  FARNHAM,  General  Electric  Co.,  Nela  Park,  Cleveland,  Ohio. 

O.  M.  GLUNT,  Bell  Telephone  Laboratories,  Inc.,  New  York,  N.  Y. 

A.  N.  GOLDSMITH,  Radio  Corporation  of  America,  570  Lexington  Ave.,  New 

York,  N.  Y. 

W.  C.  HUBBARD,  General  Electric  Vapor  Lamp  Co.,  Hoboken,  N.  J. 
R.  F.  MITCHELL,  Bell  &  Howell  Co.,  1801  Larchmont  Ave.,  Chicago,  111. 
J.  H.  KURLANDER,  Westinghouse  Lamp  Co.,  Bloomfield,  N.  J. 
W.  C.  KUNZMANN,  National  Carbon  Co.,  Cleveland,  Ohio. 
E.  HUSE,  Eastman  Kodak  Co.,  6706  Santa  Monica  Ave.,  Hollywood,  Calif. 
L.  C.  PORTER,  General  Electric  Co.,  Nela  Park,  Cleveland,  Ohio. 
E.  I.  SPONABLE,  Fox  Film  Corp.,  850  Tenth  Ave.,  New  York.  N.  Y. 


April  24-28,  inclusive;  New  York,  N.  Y. 

At  the  meeting  of  the  Board  of  Governors  held  on  October  5  at  New  York, 
plans  for  the  Spring,  1933,  Convention  were  initiated:  the  meeting  is  to  be  held 
at  New  York,  N.  Y.,  and  of  five  days  duration — April  24  to  28,  inclusive. 

Mr.  W.  C.  Kunzmann,  chairman  of  the  Convention  Committee,  assisted  by 
Mr.  H.  Griffin,  chairman  of  the  Local  Arrangements  Committee,  is  proceeding 
with  arrangements  to  hold  the  Convention  at  the  Hotel  Pennsylvania,  in  the 
Salon  Moderne. 

Mr.  O.  M.  Glunt,  chairman  of  the  Papers  Committee,  promises  an  extremely 
interesting  schedule  of  papers;  the  number  of  papers  to  be  presented  will  be 
limited  to  what  can  be  accommodated  in  the  allotted  time  without  haste  or  crowd- 
ing, a  feature  that  will  assist  considerably  in  the  selection  of  papers  from  the  point 
of  view  of  technical  quality,  with  less  emphasis  on  quantity. 

An  exhibit  of  newly  developed  motion  picture  equipment  will  be  held,  as  at 
past  Conventions,  which  should  prove  of  considerable  interest  to  every  one 
interested  in  motion  picture  engineering.  Manufacturers  of  equipment  are 
invited  to  communicate  with  the  General  Office  of  the  Society,  33  W.  42nd  St., 
New  York,  N.  Y.,  for  information  regarding  the  regulations  of  the  exhibit  and 
arrangements  for  space. 

Plans  are  being  made  to  assist  out-of-town  visitors  to  the  Convention  to  pass 
an  interesting  time  while  in  New  York,  and  special  film  programs  and  trips  of 
interest  will  be  arranged  for.  Full  details  of  the  program,  including  hotel  rates 
and  other  pertinent  information  will  be  mailed  to  the  members  of  the  Society  at  a 
later  date.  Members  and  friends  of  the  Society  are  urged  to  make  every  effort  to 
attend  the  Convention. 


At  a  meeting  of  the  Section  held  on  December  14  at  the  Walt  Disney  Studios 
in  Hollywood,  several  descriptions  of  the  technical  processes  involved  in  producing 
animated  cartoons  were  presented.  Chairman  E.  Huse  announces  an  interesting 
series  of  meetings  for  the  coming  season,  and  all  members  of  the  Section  are  urged 
to  attend  the  meetings  regularly  and  contribute  to  the  activities  of  the  Section ; 
all  meetings  will  be  open  to  both  members  and  friends. 


Reports  of  the  work  of  the  two  sub-committees  of  the  Committee  on  the  Care 
and  Development  of  Film,  one  dealing  with  exchange  practices  and  the  other 
with  laboratory  practices,  have  practically  been  completed  and  will  be  published 


in  the  JOURNAL  in  the  next  month  or  so.  This  work  represents  a  new  activity  of 
the  Society,  begun  hardly  a  year  ago,  in  collecting  all  the  important  data  on 
current  practices  in  the  handling  of  film  in  the  exchanges  and  in  the  laboratories. 
Much  yet  remains  to  be  done,  of  course,  particularly  in  the  matter  of  paving  the 
way  toward  standardization  of  technic;  the  work  of  this  year,  however,  was 
directed  more  toward  determining  the  nature  of  present  technic  and  correlating 
and  reconciling  divergent  technics. 


In  the  November  issue  of  the  JOURNAL  the  report  of  the  Committee  on  Standards 
and  Nomenclature,  which  was  presented  before  the  Society  at  the  Washington 
Convention  last  October  and  returned  to  the  Committee  for  further  consideration, 
was  published.  Accompanying  the  report  was  an  invitation  to  all  readers  of  the 
Journal  who  might  be  interested  in  motion  picture  standardization  to  submit 
in  writing  to  the  General  Office  of  the  Society,  comments  on  or  criticisms  of  the 
report.  Action  of  the  Board  of  Governors  of  the  Society  will  be  taken  at  their 
next  meeting,  on  January  20  at  Rochester,  N.  Y.,  toward  the  validation  or 
rejection  of  the  proposed  standards  in  the  light  of  the  comments  received.  Those 
who  desire  to  comment  on  the  report  are  urged  to  do  so  immediately,  so  that  their 
communications  may  be  received  in  time  for  the  consideration  of  the  Board. 


Bausch  &  Lomb  Optical  Co. 
Burnett-Timken  Laboratories 

Eastman  Kodak  Co. 

Electrical  Research  Products,  Inc. 

RCA  Victor  Co.,  Inc. 




By  action  of  the  Board  of  Governors,  October  4, 1931,  this  Honor  Roll  was  estab- 
lished for  the  purpose  of  perpetuating  the  names  of  distinguished  pioneers  who  are 
now  deceased: 






Type  3S  Com- 
plete Record- 
ing Equipment. 

Single  or  Double  System,  Variable 

Density  or  Variable  Area,  Studio 

or  Portable. 

Write  or  cable  for  literature 


3333  Belmont  Ave. 
Chicago,  U.  S.  A. 

Cable  Address:    JENKADAIR 


The  Type  652  Volume  Control  is  a  slide-wire  type 
of  attenuator  combining  compactness  and  low  cost 
with  excellent  electrical  and  mechanical  properties. 
It  uses  a  ladder-type  network  which  has  a  linear  at- 
tenuation characteristic  and  nearly  constant  impedance. 
The  noise  level  is  extremely  low. 

Impedance:     50,  200,  or  500  ohms. 

Infinite  attenuation,  linear  from  0  to  45  decibels. 

Price:     $12.50. 

For  complete  details,  address  the  General  Radio  Company,  Cambridge,  Mass. 




Manufacturers  of  motion  picture  equipment  and  supplies  are  requested  to  send 
to  the  General  Office  of  the  Society  copies  of  their  descriptive  pamphlets,  book- 
lets, and  catalogues  as  issued.  Notices  of  the  issuance  of  this  material  will  be 
published  in  the  JOURNAL,  advising  the  readers  that  the  material  may  be  obtained 
free  of  charge  by  addressing  the  manufacturers  named.  This  editorial  service 
has  been  established  in  order  to  acquaint  readers  of  the  JOURNAL  with  the  com- 
mercial developments  of  the  motion  picture  industry  as  quickly  as  they  occur. 




Volume  XX                       FEBRUARY,  1933 

Number  2 

The  Photronic  Photographic  Exposure  Meter. 


W.  N.  GOODWIN,  JR.       95 
Musical  Acoustics  of  Auditoriums  P.  CAPORALE     119 

A  New  Western  Electric  Double  Film  Portable  Sound  Record- 
ing System                                                                  C.  "R.DATT.v     128 

Engineering  and  Scientific  Charts  for  Lantern 
List  of  Members 

Slides  142 


Book  Review  



.       173 



Society  Announcements  






Board  of  Editors 

J.  I.  CRABTREE,  Chairman 



Published  monthly  at  Easton,  Pa.,  by  the  Society  of  Motion  Picture  Engineers. 

Publication  Office,  20th  &  Northampton  Sts.,  Easton,  Pa. 
General  and  Editorial  Office,  33  West  42nd  St.,  New  York,  N.  Y. 

Copyrighted,  1933,  by  the  Society  of  Motion  Picture  Engineers,  Inc. 

Subscription  to  non-members,  $12.00  per  annum;  to  members,  $9.00  per  annum, 
included  in  their  annual  membership  dues;  single  copies,  $1.50.  A  discount 
on  subscriptions  or  single  copies  of  15  per  cent  is  allowed  to  accredited  agencies. 
Order  from  the  Society  of  Motion  Picture  Engineers,  Inc.,  20th  and  Northampton 
Sts.,  Easton,  Pa.,  or  33  W.  42nd  St.,  New  York,  N.  Y. 

Papers  appearing  in  this  Journal  may  be  reprinted,  abstracted,  or  abridged 
provided  credit  is  given  to  the  Journal  of  the  Society  of  Motion  Picture  Engineers 
and  to  the  author,  or  authors,  of  the  papers  in  question. 

The  Society  is  not  responsible  for  statements  made  by  authors. 

Entered  as  second  class  matter  January  15,  1930,  at  the  Post  Office  at  Easton, 
Pa.,  under  the  Act  of  March  3,  1879. 


W.  N.  GOODWIN,  JR.** 

Summary. — This  paper  describes  a  new  photographic  exposure  meter,  which 
measures  the  brightness  of  the  scene  to  be  photographed.  It  utilizes  for  its  light 
measuring  element  two  Weston  photronic  photoelectric  cells  connected  in  parallel 
to,  and  mounted  in  the  same  case  with,  a  permanent  magnet  movable  coil  indicating 
instrument  calibrated  in  units  of  brightness:  candles  per  sq.  ft.  The  cells  are  of 
the  direct  action  dry  disk  type,  which  transform  light  energy  directly  into  electrical 
energy,  requiring  no  battery,  and  having  an  unlimited  life.  They  are  mounted  in 
tubular  depressions  to  limit  the  area  of  the  scene  covered. 

A  simple  mechanical  dial  calculator  attached  to  the  meter  case  translates  light 
values  into  exposure  values  by  a  single  setting  of  a  dial,  after  having  set  the  calculator 
once  for  all  for  the  speed  of  the  film  being  used.  The  calculator  has  the  novel  feature 
of  providing  means  for  fitting  the  brightness  range  of  a  scene  as  determined  by  its 
darkest  and  brightest  objects,  to  the  correct  film  range  indicated  on  the  dial  as  lying 
between  the  darkest  and  brightest  objects  which  the  film  will  correctly  expose,  for  the 
indicated  shutter  speed  and  aperture. 

There  is  probably  no  problem  encountered  by  the  photographer 
that  is  more  troublesome  than  that  of  determining  the  correct 
exposure.  Even  after  long  experience  one  is  usually  in  doubt  in 
estimating  exposure,  especially  at  times  other  than  mid-day  and  for 
any  but  the  most  usual  subjects.  For  such  conditions,  estimates 
made  visually  are  little  more  than  guesswork.  The  very  fact  that 
the  human  eye  is  capable  of  adapting  itself  automatically  to  such 
extreme  variations  in  light  intensities  makes  it  exceedingly  in- 
accurate as  a  means  for  judging  the  relatively  narrow  range  of  light 
values  for  correct  exposure,  especially  under  unusual  conditions. 

Light  tables,  which  give  average  values  arranged  according  to 
months,  time  of  day,  and  character  of  lighting,  are  in  extensive  use; 
but  they  fail  during  early  morning  and  late  afternoon,  and  under 
unusual  and  abnormal  conditions.  While  it  is  a  fact  that  modern 
films  have  a  wide  latitude,  or  film  range,  as  it  is  termed  in  this  paper, 
the  actual  scene  exposure  range,  or  choice  of  exposure,  is  very  narrow, 

*  Received  by  the  editor,  September  28,  1932. 
**  Weston  Electrical  Instrument  Corp.,  Newark,  N.  J. 



W.  N.  GOODWIN,  JR. 

[J.  S.  M.  P.  E. 

as  will  be  referred  to  later  in  detail.  It  is  for  this  reason  that  among 
the  many  exposures  one  makes,  only  a  few  are  really  satisfactory, 
as  every  photographer  knows. 

To  obtain  correct  exposure,  therefore,  it  is  necessary  to  be  able 
to  measure  the  actual  light  intensities  at  the  time  the  exposure  is 
to  be  made. 

FIG.  1.     Front  view  of  meter. 

The  exposure  meter  described  in  this  paper  utilized  for  its  light 
measuring  element  two  Weston  photronic  photoelectric  cells.  These 
are  of  the  direct  action,  dry  disk  type,  in  which  the  light  energy  is 
transformed  directly  into  electrical  energy,  requiring  no  battery 
for  their  operation.  As  they  are  purely  electronic  in  their  action, 
their  lives  are  unlimited  as  far  as  is  known. 

FIG.  2.     Rear  view  of  meter. 

The  cells  are  directly  connected  to  an  electrical  measuring  instru- 
ment mounted  in  a  common  case  as  illustrated  in  Fig.  1  showing  a 
front  view,  and  in  Fig.  2  showing  the  cell  construction  in  the  rear. 
A  mechanical  calculator  is  provided  for  translating  the  instrument 
indications  into  exposure  values. 

Feb.,  1933] 



The  instrument  is  calibrated  to  read  in  terms  of  the  brightness 
of  the  subject  to  be  photographed,  as  this  is  the  quantity  that  de- 
termines the  intensity  of  the  illumination  falling  upon  the  plate  to 
be  exposed. 

Before  discussing  the  exposure  meter  in  detail  it  is  desirable  to 
consider  briefly  some  of  the  fundamental  relations  of  illumination 
and  exposure.  To  show  the  relation  between  the  brightness  of  the 
subject  and  the  resulting  illumination  on  the  plate  or  film  in  a  camera, 
refer  to  Fig.  3. 

Let  A  be  a  portion  of  the  subject  to  be  photographed,  which  is 
either  self-luminous  or  becomes  luminous 
as  a  result  of  reflection  of  light  from  the 
sun,  sky,  or  other  illuminant.  Assume 
that  it  has  a  uniform  brightness  of  B 
candles  per  sq.  ft.  and  that  it  is  situated  in 
a  plane  perpendicular  to  the  axis  of  the 
lens,  at  a  distance,  Dt  from  the  lens,  relative 
to  which,  the  distance  between  lens  and 
aperture  may  be  neglected.  For  simplicity 
of  illustration,  assume  a  single  lens  and 
a  diaphragm  with  a  circular  opening  having 
a  diameter,  d.  Then  the  image  of  the  sur- 
face A  ,  properly  focused  on  the  plate,  will 
have  an  area  a  at  a  distance,  F,  from  the 
lens,  all  distances  being  measured  in  the 
same  unit.  Each  point,  pi,  of  the  object 
will  produce  a  cone  of  light  rays  having 
as  a  base  the  circular  opening  of  the 

diaphragm  as  shown  by  the   solid   lines, 

FIG.  3.     Light  diagram  and 
which   again,  reunite   in   a   corresponding       illumination  in  a  camera. 

point,  p2,  of  the  image. 

The  total  luminous  intensity  of  the  surface  A  is  the  product  of 
the  area  by  the  brightness,  or  AB  candles,  and  the  intensity  in  the 
direction  of  the  lens  is  AB  cos  6  candles.  The  resulting  illumination 
at,  and  in  the  plane  of  the  diaphragm,  is 

AB  cos4  0 

foot-candles  in  accordance  with  the  well-known  laws  of  light,  where 
(D/Cos  6)  is  the  distance  of  the  object  from  the  lens,  remembering 

98  W.  N.  GOODWIN,  JR.  [j.  s.  M.  P.  E. 

that  the  light  enters  d  at  an  angle  0  with  the  normal  and  assuming 
that  all  distances  are  measured  in  feet. 

The  amount  of  light,  in  lumens  from  the  surface  A  entering  the 
diaphragm,  is  the  product  of  the  illumination  at  that  point  by  the 
area  of  the  opening,  or 

AB  cos4  6      ird* 
D*        X  4 

Part  of  this  light  is  absorbed  by,  or  reflected  from,  the  lens,  and 
only  a  part  is  available  for  the  image,  which  is  obtained  by  multi- 
plying the  total  light  by  the  transmission  factor  of  the  lens,  T; 
or  the  light  available  for  the  image  is 

AB  cos4^      Trd' 

-  £2  -  x  "4"  x  T  lumens 

Now  this  light  is  distributed  over  the  image  having  an  area  a  so 
that  the  illumination  at  a  is  the  total  light  in  lumens  divided  by  the 
area,  or 

_          AB    COS4!?  ..  «**          _, 

E  =  —  =  --  X  —  r-  X  T  foot-candles 


From  well-known  optical  laws  the  following  proportionality  holds, 

4.  =  £? 

a  ~  F* 

Substituting  for  A  /a  hi  the  above  equation  for  E,  its  equivalent 
and  rearranging  terms,  we  have 

E  =         x   cos4  e  foot-candles 

which  shows  that  the  illumination  on  the  plate  available  for  pro- 
ducing an  image  is  proportional  to  the  brightness  of  the  object, 
independent  of  its  distance  from  the  lens  except  for  its  slight  effect 
upon  the  distance  F,  which  will  be  referred  to  later,  and  inversely 
proportional  to  the  square  of  the  ratio  of  the  focal  length  of  the 
lens  to  the  diameter  of  the  diaphragm  opening.  It  also  shows  that 
the  illumination  is  not  uniform  over  the  area  of  the  plate  but,  under 
the  assumed  conditions,  falls  off  from  the  center  in  proportion  to  the 
fourth  power  of  the  cosine  of  the  angle  of  incidence  of  the  light. 

Practically  all  lenses  are  marked  by  their  manufacturers  with 
/"/numbers  or  some  function  of  them,  which  are  the  ratios  of  the 
principal  focal  length  of  the  lens  to  the  diaphragm  openings.  Call 


this  value/,  and  substitute  it  for  (F/d)  in  the  equation;  insert  the 
numerical  constants,  and  change  to  meter-candles,  which  is  the 
unit  usually  employed  in  photographic  work,  by  multiplying  by 
10.76;  we  obtain 

E  =  8.45 -«- cos4  0  meter-candles 

Assuming  an  average  angle  0  of  16  degrees  and  a  transmission 
factor  for  the  lens  of  76  per  cent,  the  measured  value  for  a  well- 
known  make  of  lens,  which,  however,  may  vary  considerably  for 
different  makes  of  lenses,  we  obtain  the  illumination  of  the  image: 


E  =  5.4  -^  meter-candles 

When  light  falls  upon  a  photographic  plate  or  film,  the  action 
upon  the  sensitized  material  depends  upon  the  intensity  of  the 
illumination  and  upon  the  time  the  light  is  allowed  to  act.  Ex- 
pressed mathematically,  the  exposure  is  e  =  Et,  where  t  is  the  time 
the  illumination  E  acts  upon  the  film  in  seconds. 

Then  substituting  the  value  for  E  deduced  above,  we  have 


e  =  Et  =  5.4-7^  meter-candle  seconds 

It  is  thus  shown  that  the  brightness  of  an  object  is  the  true  criterion 
of  exposure,  and  not  the  intensity  or  quality  of  light  falling  upon 
the  object,  as  is  frequently  used.  The  equation  further  shows  that 
the  exposure  is  inversely  proportional  to  the  square  of  the  /  number, 
as  is  well  known. 

For  objects  at  relatively  great  distances  from  the  lens,  the  /  in 
the  equation  depends  upon  the  principal  focal  length  of  the  lens, 
and  for  convenience  the  maker  of  the  camera  bases  the  //numbers 
upon  this  value.  These  //numbers  are  sufficiently  close  to  the 
actual  values  for  distances  within  10  times  the  focal  length  of  the 
lens.  The  actual  //number  for  any  distance  can  be  computed  by 
the  following  equation  derived  from  the  usual  lens  equation: 

where  /i  =  actual  //number,  /  the  marked  number,  and  n  the  ratio 
of  the  distance  from  the  object  to  the  lens,  to  the  focal  length  of  the 


W.  N.  GOODWIN,  JR. 

[J.  S.  M.  P.  E. 

We  have  considered  so  far  only  the  illumination  available  on  the 
photographic  plate  and  the  time  it  acts,  the  product  of  which  is  the 
exposure,  and  we  shall  now  discuss  briefly  the  action  of  this  exposure 
upon  the  photographic  emulsion  so  as  to  determine  the  direct  relation 
between  the  brightness  of  an  object  to  be  photographed  and  the 
resulting  effect  in  the  final  negative. 

When  light  falls  upon  a  sensitized  plate  or  film,  a  physical  change 
takes  place  that  is  well  known,  the  resulting  change  depending  upon 
the  intensity  and  color  of  the  illumination  on  the  plate  or  film; 
upon  the  time  it  acts;  and  upon  the  sensitivity  of  the  emulsion. 
When  the  plate  is  subsequently  developed,  the  sensitized  silver 
salts  that  were  acted  upon  by  light  are  reduced  to  metallic  silver, 




V&     V*     /2p,1       2      4      8      16    32      64    128   256   512 

FIG.  4.     Typical  H  &  D  characteristic  curve  of  photo- 
graphic plates  and  films. 

and  the  amount  of  reduction  is  a  function  of  the  exposure  and  the 
time  of  development.  This  effect  was  made  the  subject  of  scien- 
tific investigation  by  Hurter  and  Driffield.  They  found  that,  for  a 
given  development,  if  values  of  density  be  plotted  against  the  loga- 
rithms of  the  exposures,  a  characteristic  curve  results,  as  shown  in 
the  typical  curve  in  Fig.  4,  known  as  the  H  &  D  curve.  In  the 
straight  portion  the  relative  densities  are  proportional  to  the  loga- 
rithms of  the  exposures,  as  is  required  for  correct  rendering  of  light 
values.  Hurter  and  Driffield  further  found  that  the  actual  densities 
increase  with  the  time  of  development.  The  density  D  is  defined 
as  the  logarithm,  to  the  base  10,  of  the  opacity  of  the  film,  which 
is  the  ratio  of  the  light  incident  upon  the  film  to  that  which  passes 
through  it. 

Feb.,  1933]  PHOTRONIC  EXPOSURE  METER  101 

For  purposes  of  illustration  the  abscissas  are  designated  in  terms 
of  relative  exposure,  and  are  plotted  logarithmically,  each  value 
being  double  that  of  the  preceding  one.  Hurter  and  Driffield  found 
by  experiment  that  the  slope  of  the  curve  increases  with  the  time 
of  development  and  that  the  straight  portion,  when  extended,  swings 
around  a  point  p  which,  for  simplicity,  is  shown  as  lying  in  the  line 
of  zero  density,  but  which  frequently  lies  below  it.  The  tangent  of 
the  angle  that  the  straight  portion  makes  with  the  horizontal  is 
known  as  7  (gamma).  The  value  of  7  is  a  measure  of  the  contrast 
of  the  film ;  that  is,  it  gives  the  rate  of  change  in  density  with  respect 
to  changes  in  the  logarithm  of  the  exposure. 

The  exposure  corresponding  to  the  point  at  which  the  straight 
portion  intersects  the  horizontal  axis  is  known  as  the  inertia,  and 
its  reciprocal  is  customarily  used  as  a  measure  of  the  speed  of  the 
film.  On  the  curve  of  Fig.  4  the  inertia  is  the  exposure  corresponding 
to  the  point  p;  but  where  p  lies  below  the  line,  the  inertia  value 
moves  along  the  exposure  axis  with  changes  in  7,  showing  that  the 
emulsion  speed  varies  with  development  time. 

The  curve  may  be  divided  into  three  parts:  (1)  the  lower  end, 
which  deviates  from  a  straight  line  at  the  point  d,  known  as  the  toe. 
This  is  the  region  of  underexposure.  (2)  The  straight  portion, 
which  is  the  region  of  correct  exposure.  (3)  The  upper  portion, 
which  extends  beyond  the  straight  line  at  the  point  b  known  as  the 
shoulder,  is  the  region  of  overexposure.  These  terms  do  not  mean, 
however,  that  the  under  and  overexposure  regions  are  not  frequently 
useful  and  often  used.  Darkest  subjects  and  the  brightest  high- 
lights of  any  scene  may  well  extend  into  the  lower  and  upper  regions, 

The  curve  illustrated  is  typical  of  average  commercial  films.  It 
will  be  noted  that  the  range  of  the  film  where  correct  exposure  may 
be  obtained  represents  an  exposure  ratio  of  about  128  to  1.  This 
ratio  varies  for  different  types  of  film  and  with  the  time  of  develop- 
ment, but  for  the  purposes  of  exposure  meter  design,  this  safe  average 
value  for  the  film  range  was  used. 

Any  given  scene  to  be  photographed  consists  in  general  of  objects 
of  differing  degrees  of  brightness  and  color,  and  the  problem 'in 
exposure  is  to  adjust  properly  the  range  of  light  values  of  the  scene 
so  that  it  lies  within  the  range  of  the  straight-line  portion  of  the 
characteristic  curve.  For  example,  if  in  a  given  scene  the  ratio  of 
the  brightness  of  the  brightest  object  to  that  of  the  darkest  object 

102  W.  N.  GOODWIN,  JR.  [j.  S.  M.  P.  E. 

in  which  detail  is  desired  is  32,  say,  then  the  brightness  range  will 
be  only  one-fourth  the  film  range,  that  is,  32  divided  by  128;  and 
the  scene  range  of  32  will  be  correctly  exposed  if  it  is  placed  any- 
where on  the  128  to  1  film  range.  On  the  other  hand,  if  the  bright- 
ness range  is  approximately  128  to  1  then  the  photographer  has  no 
choice  and  the  exact  exposure  must  be  known. 

As  briefly  referred  to  earlier  in  the  paper,  modern  films  have 
great  latitude  or  film  range,  but  it  does  not  follow  that  they  have 
an  equally  great  scene  exposure  range,  that  is,  choice  of  exposure. 
In  the  example  given  above  for  the  relatively  narrow  brightness 
range  of  32  to  1,  if  this  range  is  placed  at  the  low  end  of  the  film 
range,  then  any  exposure  less  than  the  correct  value  will  result  in 
underexposure  of  the  lower  tones,  but  an  increase  in  exposure  of 
4  to  1  will  still  give  a  good  negative.  If  the  scene  range  is  set  to  give 
a  medium  density  in  the  film  range,  then  an  error  in  estimating 
exposure  exceeding  a  ratio  of  2  to  1  will  result  in  either  underexposure 
or  overexposure.  That  is,  the  scene  exposure  range  is  only  2.  It 
has  been  found  by  experience  that  in  general  even  amateurs  who 
have  had  long  experience  can  not  estimate  so  closely  as  this,  which 
no  doubt  accounts  for  so  many  poor  negatives.  For  wider  brightness 
ranges,  the  scene  exposure  range  diminishes  and  correct  estimates 
of  exposure  become  increasingly  difficult.  It  is  obvious,  therefore, 
that  some  means  of  correlating  brightness  and  film  ranges  is  necessary 
for  the  best  work,  and  it  is  for  this  purpose  that  the  present  exposure 
meter  was  developed. 


The  meter  consists  of  two  parts:  (1)  a  means,  previously  de- 
scribed, of  measuring  the  average  brightness  of  an  entire  scene  or 
the  brightness  of  any  object  in  it,  and  (2)  a  simple  calculator  for 
translating  the  measured  brightness  into  the  proper  diaphragm 
apertures  (stops)  and  shutter  speeds  for  correct  exposure. 

The  photronic  photoelectric  cells  are  arranged  in  tubular  depres- 
sions in  the  back  of  the  case,  as  shown  in  Fig.  2.  Extended  tubes 
might  have  been  used  to  limit  the  extent  of  the  scene  covered,  but 
following  a  suggestion  by  D.  R.  White  of  the  Du  Pont  Film  Mfg. 
Corp.,  thin  metal  partitions  were  used.  These  were  designed  to 
limit  the  view  to  a  cone  having  an  angle  of  about  60  degrees. 

The  cells  are  connected  in  parallel  to  an  electrical  indicating  in- 
strument of  the  permanent  magnet  movable  coil  type.  Advantage 

Feb.,  1933] 



is  taken  of  a  very  interesting  property  of  the  photronic  photoelectric 
cell.  Its  resistance  increases  greatly  as  the  incident  illumination 
is  decreased,  so  that  a  sensitive  instrument  having  a  very  high- 
resistance  movable  coil  may  be  used.  As  the  cell  resistance  is  so 
high  near  zero  light  intensity,  the  instrument  resistance  has  little 
effect  upon  the  current  output  for  low  intensities.  As  a  result  the 
scale  is  expanded  at  the  low  end  where  sensitivity  is  required.  This 












i — i — i — i    i    i    i    i    i    r~ 






.3  ohms 


20  40  60   80  100  120  140  160  180  200  220  240 


FIG.  5.     Curves  of  current  vs.  illumination  for  photronic 
photoelectric  cell. 

effect  is  illustrated  in  the  current  response  curves  of  the  cell  for 
various  external  resistances  shown  in  Fig.  5.  It  will  be  noted  that 
the  current  for  low  intensities  is  nearly  independent  of  the  resistance. 


Let  M  in  Fig.  6  be  a  surface  of  any  shape,  plane  or  curved,  and 
at  any  angle  relative  to  the  photoelectric  cell  P,  limited  only  by  the 


W.  N.  GOODWIN,  JR. 

[J.  S.  M.  P.  E. 

requirements  that  it  must  be  a  perfect  diffuser,  or  practically  so, 
of  a  uniform  brightness  of  B  candles  per  sq.  ft.,  and  that  it  is  of 
sufficient  size  and  so  located  that  no  light  enters  the  photoelectric 
cell  other  than  that  emitted  by  the  surface.  The  cell  is  located  at 
the  bottom  of  a  tube  or  its  equivalent  so  as  to  limit  the  light  incident 
upon  it  to  a  comparatively  small  solid  angle  represented  by  the 
dotted  lines. 

Let  A  be  the  total  area  covered  by  the  cell  and  dA  an  element  of 
that  area.     As  dA  is  very  small  it  can  be  considered  as  a  plane,  and 

FIG.  6. 

Light  diagram  used  in  theory  of  surface  bright- 
ness and  photronic  exposure  meter. 

since  its  brightness  is  B  candles  per  sq.  ft.  its  light  intensity  is  BdA 
candles  normal  to  the  surface.  The  illumination  at  the  cell,  normal 
to  the  direction  of  the  light  produced  by  the  area  dA,  is  then 

B  cos  <p  dA 
dE ^- 

where  <p  is  the  angle  that  the  light  beam  makes  with  the  normal  to 
the  surface,  and  r  is  the  distance  from  dA  to  the  cell.  This  radiant 
flux  entering  the  cell  produces  an  elementary  current  di  =  idE, 
where  i  =  the  current  produced  by  unit  illumination,  say,  for  1  foot- 

Feb.,  1933] 



candle  normal  to  the  direction  of  the  light,  and  is  a  function  of  the 
angle  of  incidence,  6;  of  the  cell  arrangement;  and  of  its  sensitivity. 

,.        .,„       Bi  cos  <p  dA 
di  =  idE  =  -  p-  - 

But  cos  (pdA/r2  is  the  solid  angle  subtended  by  the  projection  of 
dA  in  the  direction  of  r,  or  di  =  Bi  dai,  where  du  is  this  elementary 
solid  angle.  Then  the  current  for  the  total  area  A  is 

/  =   fsi 


This  shows  that  the  effect  upon  the  cell  is  independent  of  the 

FIG.   7.     Hemispherical  distribution  diagram 
used  in  theory  of  surface  brightness. 

shape  or  location  of  the  surface,  provided  the  limitations  referred 
to  above  are  adhered  to. 

The  integral  J*  Bi  du  can  not  be  evaluated  mathematically  for 
the  reason  that  i  can  not  be  expressed  in  general  as  a  function  of 
a?  or  of  6.  However,  it  can  be  changed  into  a  form  that  can  be 
evaluated  from  data  readily  obtained  experimentally,  as  follows: 

Referring  to  Fig.  7,  P  is  the  cell  that  is  assumed  circular,  situated 
at  the  center  of  a  hemisphere  of  unit  radius.  Consider  an  elementary 
circular  strip  dd  that  has  a  radius  sin  6,  a  circumference  of  2?r  sin  0 
and  an  area  of  2ir  sin  6  dd,  since  the  radius  is  unity.  This  is  the 
elementary  solid  angle  du  also,  since  the  radius  is  unity. 

Substituting  this  value  for  du>  in  equation  /  =  J*  Bi  da>  we  obtain 



7  =  2irB 

Bi  sin  6  dd  or 


*  sin  9  dd 


W.  N.  GOODWIN,  JR. 

[J.  S.  M.  P.  E. 

This  states  mathematically  that  the  current  /  generated  by  the 
cell  equals  2irB  tunes  the  area  of  the  curve  having  the  equation 
i  sin  6,  between  0  and  90  degrees,  which  can  be  determined  experi- 
mentally. It  is  necessary  only  to  place  the  cell  at  a  known  distance 
from  a  luminous  source  of  known  candle-power,  arrangements  being 
made  to  change  the  angle  6  from  0  to  90  degrees.  The  current  per 
foot-candle  is  then  measured  for  as  many  values  of  0  as  will  give  a 
curve  whose  area  is  to  be  computed.  Such  a  curve  is  shown  in  Fig.  8. 

This  curve  shows  that  most  of  the  area  is  included  within  an  angle 


20         30         40         50         60 



FIG.  8.  Current  generated  in  cell  of  brightness  meter  by  illumi- 
nation of  one  foot-candle  normal  to  direction  of  light,  at  angle  of 
incidence  8,  multiplied  by  sin  6. 

of  30  degrees  from  normal  incidence  and,  therefore,  for  practical 
purposes,  only  light  coming  within  this  angle  is  effective  in  pro- 
ducing an  indication.  In  deducing  this  equation  it  is  assumed  that 
the  cell  construction  is  symmetrical  about  its  axis,  which  is  not 
strictly  true  on  account  of  the  square-shaped  openings. 

The  area  of  this  curve  is  a  constant,  depending  solely  upon  the 
cell  sensitivity  and  the  construction  of  the  parts  in  which  it  is  mounted 
and,  of  course,  need  be  determined  but  once.  Call  this  constant 
K,  and  we  have  I  =  2-jrBK  or  B  =  I/2irK  candles  per  sq.  ft. 

The  electrical  instrument,  therefore,  can  be  calibrated  to  indicate 

Feb.,  1933]  PHOTRONIC  EXPOSURE  METER  107 

brightness  directly.  This  method  is  not  the  simplest  one  to  use 
but  was  described  to  illustrate  the  principle  of  the  instrument. 

Another  method  of  calibrating  or  checking  the  instrument  in 
brightness  units,  much  simpler  than  that  just  described,  is  to  direct 
the  cells  toward  a  diffusing  surface  large  enough  so  that  no  other 
light  enters  the  cell,  of  known  reflection  factor  R,  uniformly  illumi- 
nated by  a  luminous  source  of  known  candle-power  to  a  measured 
value  R  foot-candles.  The  well-known  relation  then  gives  the 
brightness  B  =  ER/ir  candles  per  sq.  ft. 

The  ordinary  scene,  of  course,  is  in  general  not  of  uniform  bright- 
ness and  when  the  meter,  calibrated  for  uniform  brightness,  is 
directed  toward  such  a  scene,  it  indicates  the  average  value.  Ex- 
perience has  shown  that  this  value  when  properly  used  gives  in  most 
cases  a  relatively  high  accuracy  in  determining  photographic  exposure, 
as  will  be  shown  later. 

The  instrument  usually  has  two  ranges,  0  to  1300  and  0  to  130 
candles  per  sq.  ft.  The  high  range  is  obtained  by  shunting  the 
low  range  through  a  contact  key,  which  is  normally  closed.  When 
the  key  is  depressed,  the  shunt  is  open-circuited  and  the  instrument 
indicates  on  the  low  range. 


The  calculator,  shown  in  Fig.  9,  consists  of  three  dials,  L,  T,  and 
E.  Dial  L  is  fixed  and  gives  the  light  values  in  candles  per  sq.  ft., 
with  numbers  from  1  to  1300  corresponding  to  those  on  the  instru- 
ment scale.  This  dial  also  contains  numbers  corresponding  to 
plate  speeds. 

Dial  T  is  the  time  dial,  graduated  in  shutter  speeds  from  1/soo 
second  to  64  seconds.  It  is  movable,  but  requires  adjustment  only 
when  the  kind  of  film  used  is  changed,  as,  for  example,  when  changing 
from  regular  to  super-panchromatic.  This  dial  is  held  in  position 
by  a  pin,  and  to  change  its  position  it  has  purposely  been  made 
necessary  to  lift  the  dial  to  the  next  pin  position  in  order  to  prevent 
accidental  displacement  without  the  knowledge  of  the  user.  It  can 
be  set  so  that  its  index  points  to  the  speed  of  the  film  being  used. 

Dial  E  is  the  working  dial,  and  requires  but  one  setting  to  determine 
an  exposure.  This  dial  contains  the  scene  positions  and  the  stop 
values,  graduated  from //1. 5  to //32. 

The  values  on  the  dials  and  their  relative  locations  depend  upon 
the  equation,  developed  above,  for  exposure;  and  upon  film  char- 

108  W.  N.  GOODWIN,  JR.  [j.  s.  M.  p.  E. 

acteristics  determined  experimentally.  They  are  based  on  the 
speed  of  high-speed  orthochromatic  film,  examples  of  which  are 
Verichrome  and  Plenachrome,  which  is  arbitrarily  given  the  number 
16.  They  increase  logarithmically,  each  division  having  a  value, 
the  effect  of  which  upon  exposure  is  approximately  equal  to  \/2 
times  that  of  the  preceding  one.  That  is,  the  effects  are  doubled 
for  every  second  division.  In  the  case  of  the  //scale,  it  is  also  the 
effect  upon  the  exposure  that  doubles  every  second  division;  there- 
fore, since  exposure  varies  with  the  square  of  the  //number  these 
numbers  double  every  fourth  division.  Any  of  the  scales  may  be 
extended  in  either  direction  indefinitely  by  counting  divisions,  re- 
membering that  the  effective  values  double  every  second  division. 

FIG.  9.     Mechanical  calculator. 

It  would  have  been  desirable  to  measure  brightness  in  metric 
units  as  is  customary  in  photographic  work,  but  these  units  gave 
unwieldly  figures  for  values  of  brightness  occurring  in  nature. 
Candles  per  sq.  ft.,  however,  gave  values  that  were  satisfactory. 
A  brightness  of  one  candle  per  sq.  ft.,  for  example,  will  produce  a 
just  visible  density  on  a  sensitive  emulsion  in  a  camera  having  an 
ordinary  fast  lens  at  the  lowest  shutter  speed  for  instantaneous 

The  calculator  is  so  designed  that  it  indicates  the  limits  of  the 
film  range  for  correct  exposure,  which  lies  between  the  positions 
marked  Darkest  Object  and  Brightest  Object,  and  provides  means  for 
properly  adjusting  the  brightness  range  of  the  scene  to  the  film 
range  so  as  to  produce  the  best  exposure.  In  this  manner  it  takes 
care  of  the  entire  range  of  light  values  in  the  subject. 

Feb.,  1933]  PHOTRONIC  EXPOSURE  METER  109 

The  position  designated  Darkest  Object  Correctly  Exposed*  is  so 
located  that,  when  set  to  any  light  value,  an  object  having  that 
brightness,  when  used  with  the  indicated  values  of  stop  and  shutter 
speed,  will  result  in  an  exposure  on  the  plate  or  film  corresponding 
to  the  lower  end  of  the  straight  portion  of  the  characteristic  curve. 
The  position  designated  Brightest  Object  Correctly  Exposed  in  a 
similar  manner,  when  set  to  any  light  value,  indicates  values  of  stop 
and  shutter  speed  which,  for  objects  having  that  light  value,  will 
result  in  an  exposure  corresponding  to  the  upper  end  of  the  straight 
portion  of  the  characteristic  curve. 

This  may  be  visualized  by  assuming  a  strip  of  the  photographic 
film  or  plate  placed  around  the  circumference  of  the  light  value 
dial  L,  and  that  the  dial  E  is  set  to  any  position  relative  to  dial  L. 
Then,  using  the  shutter  speed  and  aperture  indicated  for  this  posi- 
tion, if  the  film  could  be  exposed  at  each  light  value  division  on  dial 
L  by  the  light  from  an  object  of  corresponding  brightness,  there  will 
result,  after  development,  a  variation  in  density  along  the  strip. 
This  increases  in  equal  increments  for  the  light  values  lying  between 
the  Darkest  Object  and  Brightest  Object  arrows  on  dial  E,  from  the 
minimum  correct  density  at  the  Darkest  Object  arrow  to  the  maxi- 
mum correct  density  at  the  Brightest  Object  arrow.  For  light  values 
below  and  above  these  arrows  the  density  does  not  change  pro- 
portionally, and  those  portions  of  the  film  are  in  the  underexposed 
and  overexposed  regions,  respectively. 

This  is  true  for  any  position  of  the  dial  E  when  the  indicated 
shutter  speed  and  aperture  for  that  position  are  used,  and  thus  the 
calculator  provides  a  means  of  placing  the  brightness  range  of  a 
scene  on  the  correct  density  range  of  the  emulsion. 


In  any  scene  to  be  photographed,  therefore,  if  one  can  measure 
the  brightness  of  the  darkest  and  brightest  objects  in  which  detail 
is  desired,  it  is  necessary  only  to  set  the  dial  E  so  as  to  include  these 
extremes  of  scene  light  values  on  dial  L  anywhere  between  the 
Darkest  Object  and  Brightest  Object  arrows  on  dial  E,  and  a  correct 

*  Since  this  paper  was  written  the  designations  on  the  calculator  dial  have 
been  changed  with  the  idea  of  making  their  meaning  more  clear,  as  follows: 
Brightest  Object  Correctly  Exposed  is  changed  to  Brighter  Objects  Will  Be  Over- 
exposed and  Darkest  Object  Correctly  Exposed  to  Darker  Objects  Will  Be  Under- 

110  W.  N.  GOODWIN,  JR.  [j.  s.  M.  p.  E. 

exposure  will  result,  if  the  indicated  shutter  speed  and  aperture 
are  used. 

If  the  dial  E  is  set  so  that  the  brightness  range  comes  at  the  lower 
end  of  the  film  range,  then  the  average  density  of  the  film  will  be 
low,  and  it  will  be  a  quick-printing  film;  if  the  brightness  range  is 
set  midway  in  the  film  range,  the  film  will  have  a  medium  density; 
and  if  set  at  the  upper  part,  the  film  will  have  the  maximum  safe 
density  and  will  be  a  slow-printing  film.  This  method  affords  the 
photographer  a  means  of  obtaining  exposures  of  any  desired  density 
within  reasonable  limits. 


It  is  usually  quite  sufficient  in  ordinary  scenes  to  measure  the 
brightness  of  the  darkest  object  or  darkest  shadow  in  which  detail 
is  desired  if  these  can  be  approached  sufficiently  close  to  be  measured, 
and  then  set  the  Darkest  Object  arrow  to  the  value  of  the  mea- 
sured light  value  and  adjust  the  camera  to  the  indicated  shutter 
speeds  and  aperture. 

All  objects  in  the  scene  will  then  be  correctly  exposed  up  to  the 
brightest  objects,  provided  the  brightness  of  these  objects  does  not 
exceed  the  limit  of  the  film  range,  which  is  about  128  times  that  of 
the  measured  value  of  the  darkest  object  and  indicated  by  the  value 
opposite  the  Brightest  Object  position  on  the  dial.  For  example, 
suppose  that  a  building  is  to  be  photographed  and  that  it  is  desired 
to  obtain  details  in  the  shadows,  which  are  found  by  measurement  to 
have  a  brightness  of,  say,  4  candles  per  sq.  ft.  Then  setting  the 
Darkest  Object  position  to  4,  it  will  be  observed  by  referring  to  the 
dial  E  that  all  objects  in  the  scene  having  a  brightness  up  to  500 
candles  per  sq.  ft.,  if  any  are  present,  will  be  correctly  exposed  if  the 
indicated  exposure  is  given.  This  upper  value  is  greater  than  is 
usually  found  in  such  a  scene.  When  the  brightness  of  the  brightest 
object  is  considerably  less  than  that  indicated  as  the  Brightest  Object 
Correctly  Exposed,  then,  as  referred  to  above,  the  general  density 
level  of  the  film  may  safely  be  increased,  if  desired,  by  increasing 
the  exposure,  provided  the  brightness  of  the  brightest  object  in 
the  scene  does  not  exceed  the  value  indicated  on  dial  L  as  the  Brightest 
Object  Correctly  Exposed. 


When  the  brightness  of  a  dark  colored  object  in  the  shade  is  very 
low  so  that  it  can  not  be  measured  with  accuracy  on  the  instrument, 

Feb.,  1933]  PHOTRONIC  EXPOSURE  METER  111 

or  possibly  not  at  all,  its  approximate  value  may  often  be  determined 
by  the  following  substitution  method: 

The  object,  as,  for  example,  the  trunk  of  a  tree  in  the  woods  or 
the  side  of  a  dark  colored  building,  usually  has  one  side  or  a  part 
well  illuminated;  and  if  not,  similar  objects  in  the  vicinity  may  have. 
Measure  the  brightness  of  the  lighter  side,  then  place  a  white  or  a 
light  colored  surface,  such  as  a  sheet  of  paper  of  ordinary  letter 
size,  on  the  same  part  of  the  surface  where  the  first  measurement  was 
made,  and  measure  its  brightness.  The  ratio  of  the  two  readings 
gives  the  ratio  of  the  reflection  coefficients  of  the  paper  and  the 
object.  Then  place  the  paper  on  the  dark  side,  the  brightness  of 
which  is  desired,  and  again  measure  its  brightness.  The  brightness 
of  the  dark  object  can  then  be  computed  by  dividing  the  paper 
brightness  just  measured  by  the  ratio  found  in  the  first  measurement. 
For  example,  assume  a  scene  under  trees,  the  darkest  object  of 
which  is  the  trunk  of  a  tree,  the  details  of  which  are  to  be  rendered 
in  the  photograph.  As  is  often  the  case,  spots  of  sunlight  illuminate 
parts  of  the  tree  trunk,  or  that  of  some  similar  tree ;  measurement  of 
a  bright  spot  gives,  say,  50  candles  per  sq.  ft.  Placing  a  sheet  of 
white  paper  on  the  same  spot  gives  a  brightness  of,  say,  600.  The 
ratio  of  the  reflection  coefficients  is  then  12.  Now,  placing  the  sheet 
of  paper  on  the  dark  side,  and  finding  it  to  measure,  say,  3  candles 
per  sq.  ft.,  it  follows  that  the  brightness  of  the  dark  side  is  8  divided 
by  12  or  J/4  candle  per  sq.  ft.  The  position  on  the  calculator  dial  L 
for  this  value  is  at  the  fourth  division  below  1. 


In  very  dark  subjects,  such  as  interiors,  dark  ravines,  etc.,  where 
the  darkest  objects  are  so  much  less  bright  than  1  candle  per  sq.  ft. 
that  they  can  not  be  measured  by  the  instrument,  and  where  the 
substitution  method  is  not  convenient,  the  brightest  object  in  the 
scene  in  which  detail  is  desired  may  be  measured,  and  the  arrow  on 
dial  E  designated  Brightest  Object  set  to  the  measured  light  value. 
Then,  setting  the  camera  to  the  indicated  stop  and  shutter  speed, 
all  darker  objects  in  the  scene  down  to  Ymth  the  brightness  of  the 
object  measured  will  be  correctly  exposed.  In  using  this  method, 
accidental  highlights,  such  as  windows  looking  outdoors,  or  sun 
spots  in  ravines,  etc.,  should  not  be  measured  as  the  brightest  object. 
This  method  is  limited  by  the  fact  that  the  meter  is  not  sensitive 
to  light  values  less  than  about  1  candle  per  sq.  ft.,  which  is  the  bright- 

112  W..N.  GOODWIN,  JR.  [j.  s.  M.  P.  E. 

ness  of  a  white  surface  placed  about  4.5  feet  from  a  60- watt  lamp. 
This  limitation  is  the  result  of  the  otherwise  very  desirable  feature 
of  a  small  and  compact  size.  However,  in  such  scenes,  especially 
interiors,  the  photographer  usually  increases  the  illumination  for 
better  effects  and  the  meter  can  be  used.  If  no  object  is  bright 
enough  to  give  an  indication,  then  frequently  a  sheet  of  white  paper 
may  be  properly  placed  and  used  as  a  test  object. 


There  are  many  situations  in  which  it  is  not  convenient,  if  not 
impossible,  to  approach  sufficiently  close  to  the  darkest  or  brightest 
objects  to  measure  their  brightness.  In  such  cases  it  is  necessary 
to  measure  the  average  brightness  of  the  entire  scene  by  directing 
the  meter  toward  it.  In  any  case,  however,  the  problem  is  still 
to  determine  the  brightness  range  of  the  scene,  and  to  do  this  it 
is  necessary  to  know  the  ratio  of  the  average  value  to  that  of  the 
darkest  and  brightest  objects  in  which  detail  is  desired.  This, 
however,  is  the  problem  for  the  instrument  designer,  and  is  auto- 
matically taken  care  of  in  the  calculator.  As  the  result  of  experience 
it  has  been  found  that,  if  all  scenes  are  divided  into  three  classes, 
this  brightness  ratio  can  be  predetermined  for  each  class  with  suffi- 
cient accuracy  for  most  practical  purposes.  The  three  classes  of 
scenes  have  been  designated  A — Distant  or  Weak  Contrast,  B — Normal, 
and  C — Dark  and  Strong  Contrast.  Scenes  A  consist  usually  of  those 
having  a  high  brightness  level  and  weak  contrast,  such  as  clouds 
and  distant  scenes,  and,  as'  can  be  computed  by  counting  the  di- 
visions on  dial  L  indicated  by  dial  E,  Fig.  9,  the  ratio  of  the  average 
brightness  to  the  darkest  object  that  could  be  correctly  exposed, 
if  it  were  present,  is  6  to  1. 

Scenes  C  consist  of  dark  streets,  ravines,  etc.,  where  the  general 
level  of  brightness  is  low,  even  at  midday,  with  no  bright  highlights ; 
and  also  of  scenes  where  the  contrast  is  extreme,  in  which  the  ratio 
of  the  brightest  to  the  darkest  objects  approaches  the  limits  of  the 
safe  film  range,  128  to  1,  where  it  is  desired  to  obtain  detail  in  the 
dark  objects  even  at  the  expense  of  overexposing  the  highlights. 

For  such  scenes  the  calculator  provides  a  ratio  of  average  value 
to  darkest  object  of  48  to  1. 

Scenes  B  represent  those  not  included  in  A  and  C,  and  are  the 
usual  normal  subjects.  In  these  the  highlights  and  shadows  are 
not  extreme,  and  are  about  evenly  divided.  The  calculator  provides 

Feb.,  1933]  PHOTRONIC  EXPOSURE  METER  113 

for  a  ratio  of  average  brightness  to  that  of  the  darkest  object  of 
16  to  1,  and  a  ratio  of  brightest  object  to  average  of  8  to  1. 

It  may  be  of  interest  to  know  the  approximate  values  of  brightness 
of  some  of  the  usual  objects  in  nature.  These  are  given  in  Table  I. 


Approximate  Brightness  of  Familiar  Objects 

Objects — near  Midday  Candles  per  Sq.  Ft. 

Clear  Blue  Sky — Summer  250-  350 

Blue  Sky  with  White  Clouds  400-  800 

Sky  with  Light  Haze  1000 

Light  Buildings  in  Sun  150-1000 

Light  Buildings  in  Shade  20-    40 

Green  Foliage  in  Sun  100 

Cement  Sidewalk  in  Sun  200-  600 

Cement  Sidewalk  in  Shade  30 

Average  Distant  Scenes  300-  700 

Average  Normal  Scenes  100-  250 

Average  Dark  Scenes  Up  to  80 

Under  Trees,  Dense  Foliage  Up  to  10 


As  is  well  known,  the  photographic  sensitive  material  is  not 
equally  sensitive  to  all  colors  even  in  panchromatic  films,  and  further, 
the  various  sources  of  illumination  differ  greatly  in  the  relative 
amounts  of  the  different  colors  that  they  radiate.  For  example, 
tungsten  illumination  has  relatively  little  blue  and  green  but  is 
rich  in  yellow  and  red  rays,  whereas  sunlight  has  relatively  much 
more  blue  and  green. 

In  Fig.  10,  curves  are  given  showing  the  spectral  response  of  the 
photronic  photoelectric  cell;  the  spectral  sensitivity  of  the  normal 
human  eye,  known  as  the  visibility  curve;  and  the  spectral  dis- 
tribution of  energy  radiated  from  various  sources,  all  computed  to 
have  the  same  visual  intensity  by  the  following  method: 

Relative  spectral  energy  curves  for  the  corresponding  color  tem- 
peratures were  taken  from  Critical  Tables  at  arbitrary  energy  levels 
and  the  luminosity  curves  obtained  for  each  by  multiplying  the 
ordinates  of  each  curve  by  those  of  the  visibility  curve  at  corre- 
sponding wavelengths.  These  curves  were  then  integrated  by  de- 
termining the  area  included  under  each,  to  obtain  the  luminosity 
from  each  source,  which  follows  from  the  equation 



W.  N.  GOODWIN,  JR. 

[J.  S.  M.  P.  E. 

Where   L     =  luminosity 

jEx  =  relative  radiant  flux  at  wavelength  X 
and         Fx  =   visibility  function  at  X 

In  general,  these  areas  will  not  be  equal,  but  for  the  same  visual 
intensity  they  must  be  equal;  therefore,  one  of  the  spectral  energy 
curves  was  assumed  as  the  standard  and  all  the  ordinates  of  each  of 
the  others  were  changed  in  the  ratio  of  the  area  of  the  luminosity 
curve  of  the  standard  to  the  area  of  the  corresponding  luminosity 
curve  of  each  of  the  others. 

Spectral  energy  curves  drawn  with  these  computed  ordinates 









P  40 


K  EAI J  Ni  )ON 














FIG.  10.     Photronic  photoelectric  cell  spectral  response,  and  spectral  energy 
distribution  of  various  illuminants  of  equal  visual  intensity. 

as  given  in  Fig.  10,  therefore,  all  produce  the  same  luminous  intensity. 

The  current  generated  in  the  photronic  photoelectric  cell  by  the 

special  distribution  of  radiation  corresponding  to  these  curves  is 



Where   /     =  the  current  generated 

jEx  =  radiant  flux  per  unit  X  at  X 

Px  =  current  generated  per  unit  radiant  flux  at  X 

Feb.,  1933] 



To  determine  the  current,  therefore,  it  is  necessary  only  to  form 
the  current  distribution  curves  by  multiplying  the  ordinates  of  the 
photronic  photoelectric  cell  response  curve  by  those  of  the  spectral 
energy  curves  at  corresponding  wavelengths,  and  to  integrate  them. 
This  has  been  done,  and  it  is  interesting  to  find  that  the  three  sources, 
tungsten  at  3000°K.,  mean  noon  sun,  and  equivalent  daylight  at 
5400°K.,  all  produce  the  same  current  output  from  the  cell  for  the 
same  visual  intensity,  within  a  small  percentage,  which  in  the  above 
computation  was  21/z  per  cent.  This  has  been  corroborated  by  actual 







FIG.  11.  Sensitivity  of  high-speed  panchromatic  film  and  spectral  energy 
distribution  of  various  illuminants  of  equal  visual  intensity,  after  passing 
through  a  lens. 

tests  for  sunlight  and  tungsten  at  3000°K.  to  within  the  limits  of 
experimental  error. 

Fig.  11  shows  the  spectral  distribution  of  energy  from  the  various 
sources  reaching  the  photographic  film  after  passing  through  an 
average  lens.  These  curves  are  obtained  by  multiplying  the  ordi- 
nates of  the  corresponding  curves  in  Fig.  10  by  the  spectral  trans- 
mission of  a  lens,  the  values  for  which  were  obtained  from  a  paper  by 
L.  A.  Jones1  published  in  the  JOURNAL. 

Fig.  11  also  shows  the  spectral  sensitivity  of  high-speed  pan- 
chromatic film  as  given  by  Jones.2  The  ordinates  of  this  curve  are 

116  W.  N.  GOODWIN,  JR.  [j.  s.  M.  P.  E. 

proportional  to  the  reciprocals  of  the  radiant  energy  required  to 
produce  a  density  of  unity  in  the  developed  negative. 

It  will  be  observed  by  referring  to  this  curve  that  the  human  eye 
is  not  nearly  so  sensitive  to  blues  and  greens  as  is  the  photographic 
film.  On  the  other  hand,  Fig.  10  shows  that  the  photronic  cell  is 
much  more  sensitive  to  these  colors  and  also  to  the  reds,  than  the 
eye,  and  for  this  reason  its  indications  in  an  exposure  meter  are 
more  accurate  than  estimates  by  the  eye. 

In  order  to  compare  estimates  of  exposure  by  the  eye  with  those 
by  the  photronic  exposure  meter  for  various  illuminants  and  for 
various  colors,  photographic  intensities  were  computed  for  daylight 
(mean  noon  sun),  tungsten  illumination  at  3000 °K.,  and  for  four 
representative  colors  in  monochromatic  light — blue  at  470  m/z, 
green  at  520  mju,  yellow  at  580  mju,  and  red  at  650  mju.  The  photo- 
graphic intensities  were  computed  for  two  conditions:  (1)  for  equal 
indications  on  the  photronic  exposure  meter,  and  (2)  for  equal 
visual  intensity,  that  is,  as  judged  by  the  eye  by  photometric  methods 
or  otherwise. 

The  photographic  intensities  of  the  light  for  the  same  indications 
on  the  exposure  meter  from  mean  noon  sun  and  from  tungsten  at 
3000°K.  for  high-speed  panchromatic  film  were  determined  by 
multiplying  the  ordinates  of  the  spectral  energy  curves  by  corre- 
sponding ordinates  of  the  spectral  sensitivity  of  the  film  in  Fig.  11 
and  integrating.  For  monochromatic  light,  the  intensity  of  the 
radiation,  at  the  desired  wavelengths,  required  to  produce  the  same 
indication  on  the  exposure  meter  as  for  mean  noon  sun  of  the  spectral 
energy  level  in  Fig.  11  used  as  a  standard,  was  determined  by  di- 
viding the  photographic  intensity  of  mean  noon  sun  as  computed 
above,  by  the  ordinate  of  the  photronic  photoelectric  cell  response 
curve  at  the  desired  wavelength;  then  multiplying  the  radiation 
intensity  thus  obtained  by  the  sensitivity  ordinate  at  that  wave- 
length of  the  spectral  response  of  the  film. 

The  photographic  intensity  for  the  same  visual  intensity  is  de- 
termined in  the  same  manner  as  that  just  described  for  equal  pho- 
tronic exposure  meter  indications,  except  that  instead  of  using  the 
photronic  cell  response  curve,  the  visibility  or  eye  response  curve  is 
used.  The  results  are  tabulated  in  Table  II,  and  give  the  ratio  of 
the  amount  of  radiation  at  each  wavelength  to  that  which  will 
result  in  a  film  density  of  unity,  compared  with  daylight  as  a  stand- 
ard. For  example,  estimates  by  the  eye  for  blue  will  give  an  ex- 

Feb.,  1933]  PHOTRONIC  EXPOSURE  METER  117 

posure  four  times  the  correct  value,  and  for  yellow  slightly  over 
!/4,  or  a  range  of  about  16  to  1  in  a  scene;  whereas  the  photronic 
exposure  meter  gives  nearly  correct  values  for  the  blue  and  red  and 
half  or  slightly  less  for  the  yellow  and  green,  or  a  range  of  about 
2  to  1  in  a  scene. 


Photographic  Intensity  Resulting  from  Exposure  as 

Determined  by 

Color  or  X  Photronic 

Source  m/a  Eye  Exposure  Meter 

Daylight  ...  1.0  1.0 

Tungsten  ...  0.81  0.81 

Blue  470  4.0  1.1 

Green  520  0.35  0.53 

Yellow  580  0.27  0.41 

Red  650  2.5  1.1 

Monochromatic  light  is,  of  course,  not  found  in  ordinary  scenes, 
as  the  colors  of  natural  objects  are  composite,  consisting  of  rather 
wide  wave-bands  and  usually  having  a  large  proportion  of  white 
light.  The  colors  selected,  however,  are  sufficiently  representative 
of  the  visible  spectrum  to  illustrate  the  difference  in  results  obtained 
by  the  two  methods.  They  show  that  the  photronic  exposure  meter 
gives  indications  that,  considering  the  latitude  of  films,  differ  rela- 
tively little  from  the  true  values  throughout  the  spectrum,  whereas 
the  eye  values  vary  through  such  a  wide  range  that  they  illustrate 
again  how  poor  the  eye  is  as  a  means  of  estimating  exposure,  even 
with  the  assistance  of  the  usual  photometric  methods. 


The  exposure  meter  calculator  and  film  speeds  are  based  upon 
illumination  equivalent  to  average  daylight.  For  other  luminous 
sources  the  film  speeds  may  be  considered  as  having  different  values 
corresponding  to  the  source,  the  kind  of  emulsion,  and  the  spectral 
response  of  the  photronic  photoelectric  cell,  and  the  calculator  may 
be  set  to  these  values. 

Owing  to  the  spectral  response  characteristic  of  the  cell,  the  speed 
values  to  be  used  with  the  meter  for  various  illuminants  will,  in 
general,  not  correspond  to  the  relative  sensitivities  of  the  emulsion 
as  supplied  by  the  manufacturer  of  the  film,  as  these  are  based  upon 
equal  visual  intensities  or  upon  equal  radiant  flux.  However,  as 
stated  above,  the  speed  values  for  average  daylight  and  tungsten 
at  3000 °K.,  by  a  happy  coincidence,  do  correspond. 

118  W.  N.  GOODWIN,  JR. 

In  a  similar  manner  when  filters  are  used  they  may  be  considered 
as  changing  the  film  speed  by  their  multiplying  constant  and  the 
calculator  may  be  set  accordingly. 

In  Table  III  are  listed  arbitrary  speed  numbers  for  various  types 
of  film,  gathered  from  various  sources  and  from  tests,  that  are  the 
best  obtainable  at  the  date  of  this  writing.  They  are  based  on  the 
speed  of  high-speed  orthochromatic  film,  which  is  given  the  number 
16.  These  values  may  require  modification  as  a  result  of  further 
experience.  A  very  excellent  contribution  to  this  subject  was  made 
by  Davis  and  Neeland  in  this  JOURNAL.3 


Film  Daylight  Tungsten 

Ordinary  Amateur  12  4 

Verichrome  or  Plenachrome  16  6 

Regular  Cine  Kodak  Panchromatic  12  6 

Super  Cine  Kodak  Panchromatic  16  12 

Commercial  Panchromatic  16  8 

Super  Panchromatic  24  16 

The  author  wishes  to  acknowledge  the  helpful  assistance  of  L.  A. 
Jones,  of  the  Eastman  Kodak  Company,  and  of  D.  R.  White,  of  the 
Du  Pont  Film  Manufacturing  Corporation,  in  developing  experi- 
mental films  under  controlled  conditions,  and  for  suggestions  referred 
to  above. 


1  JONES,  L.  A.:    "Photographic  Sensitometry,  Part  I,"  /.  Soc.  Mot.  Pict. 
Eng.,  XVII  (Oct.,  1932),  No.  4,  p.  491. 

2  JONES,  L.  A.:    "Photographic  Sensitometry,  Part  IV,"  /.  Soc.  Mot.  Pict. 
Eng.,  XVIII  (March,  1932),  No.  3,  p.  324. 

3  DAVIS,  R.,  AND  NEELAND,  G.  K. :    "Variation  of  Photographic  Sensitivity 
with  Different  Light  Sources,"  /.  Soc.  Mot.  Pict.  Eng.,  XVIII  (June,  1932),  No. 
6,  p.  732. 


Summary. — The  author  proposes  that,  on  account  of  the  variation  in  the  time 
between  beats  in  music,  more  effective  rendition  of  music  could  be  accomplished  by 
varying  the  time  of  reverberation  of  the  auditorium  or  room  in  which  the  music  is 
played.  The  relation  between  the  tempo  of  the  music  and  the  time  of  reverberation 
is  discussed,  with  particular  reference  to  the  overlapping  of  the  reverberation  from 
one  bar  of  music  to  the  succeeding  bar.  (Editor's  note:  The  reader  is  cautioned  to 
distinguish  between  the  technical  meanings  of  terms  used  in  the  paper  and  their 
meanings  in  musical  parlance;  the  footnotes  should  be  consulted  for  the  musical 

The  importance  of  increasing  the  usefulness  of  enclosures  such  as 
sound  motion  picture  studios,  recording  studios,  broadcasting  studios, 
theaters,  music  halls,  etc.,  by  controlling  the  time  of  reverberation 
is  being  recognized  more  and  more.  In  all  these  types  of  rooms 
music  of  some  form  is  performed,  and  the  control  of  reverberation 
may  add  considerably  to  the  artistic  presentation  of  such  music. 
Thus,  the  effects  of  large  tone  or  fine  definition  or  articulation  may 
both  be  achieved  by  suitable  control.  The  following  is  a  brief  dis- 
cussion of  some  of  the  important  factors  to  be  considered  in  con- 
trolling reverberation  for  musical  purposes. 

Music  is  a  unique  art  in  that  a  third  person  (or  group  of  persons) 
is  necessary  to  convey  the  composer's  thought  to  his  audience.  In 
particular  cases  it  may  happen  that  the  third  person  and  the  composer 
are  one,  as,  for  example,  when  Kreisler  plays  his  own  compositions. 
But  even  in  these  cases  Kreisler  the  violinist  is  not  the  same  as 
Kreisler  the  composer.  In  other  words,  composition  and  expression 
are  neither  the  same  nor  are  they  simultaneous.  To  speak  of  this 
situation  in  more  familiar  engineering  terms,  we  may  think  of  the 
history  of  a  musical  composition  as  divided  into  four  stages.  The 
first,  which  we  shall  call  A,  is  the  conception  of  the  composition  in 
the  mind  of  the  composer.  The  second,  B,  is  the  transcribing  of  this 

*  Received  December  15,  1932. 
**  Electro-Acoustical  Engrg.  Co.  of  America,  Philadelphia,  Pa. 




[J.  S.  M.  P.  E. 

concept  into  a  form  known  as  the  score.  The  third,  C,  is  the  trans- 
ference of  the  concept  from  the  score  to  the  mind  of  the  player,  or 
interpreter;  and  the  fourth,  D,  the  transmission  of  the  concept,  by 
means  of  sound,  to  the  audience.  It  must  be  obvious  that  in  such  a 
complex  transition  it  is  rare  that  a  listener  will  sense  the  same  musical 
thought  (i.  e.,  the  same  physical  sound  as  conceived  originally)  that 
the  composer  had  in  mind,  and  we  may  therefore  speak  (rather 
loosely,  of  course)  of  the  efficiencies  of  the  various  stages  of  the  transi- 
tion. For  example,  there  are  some  effects  that  can  not  be  indicated 
by  the  usual  musical  notation;  hence  the  efficiency  of  transition  B  is 
less  than  unity.  Similarly,  the  score  may  be  ambiguous  in  certain 



FIG.   1.     Duration  of  musical  beats  for  various  metronome  settings 
(Metronome  de  Maelzel). 

parts,  or  in  some  respects ;  therefore,  the  efficiency  of  transition  C  is 
also  less  than  unity.  Very  little  has  been  done  to  increase  these 
various  efficiencies.  Reverberation  control,  however,  offers  the 
possibility  of  increasing  the  efficiencies  of  both  transitions  B  and  D. 
The  combinations  of  sound  that  reach  the  audience  are  determined 
not  only  by  the  nature  of  the  source  of  the  sound  (orchestra,  organ, 
violin,  etc.}  but  also  by  the  character  of  the  enclosure  within  which 
the  sound  occurs  and  the  audience  is  located.  This  fact  has  been 
known  from  the  most  ancient  times,  but  no  direct  use  was  made  of 
the  knowledge.  For  instance,  when  Bach  wrote  the  Mass  in  B-minor 
he  was  acquainted  quite  intimately  with  the  acoustical  properties  of 

Feb.,  1933]  ACOUSTICS  OF  AUDITORIUMS  121 

the  Leipzig  Thomaskirche  and  could  foresee  the  approximate  effect 
of  the  music.  It  was  obviously  impossible  for  him  to  foretell  the 
effect  in  some  other  church  or  auditorium.  Recent  progress  in 
acoustics,  particularly  as  regards  reverberation,  has  made  it  possible 
to  control  the  acoustical  properties  of  an  auditorium  so  that  a  musical 
composition  may  be  rendered  in  such  a  manner  as  to  accord  very 
closely  with  the  wishes  of  the  interpreter.  Furthermore,  the  control 
of  the  auditorium  might  be  placed  in  the  hands  of  the  composer,  so 
that  not  only  is  efficiency  D  increased,  but  also  that  of  B;  or,  more 
specifically,  the  composer  might  indicate  on  the  score  just  what  the 
acoustical  conditions  should  be  for  any  particular  passage. 

The  technical  problem  of  controlling  reverberation  is  this:  given  an 
auditorium  having  a  certain  volume  and  exposed  wall  surface,  to 
vary  the  total  sound  absorption  of  the  room  so  as  to  vary  its  period  of 
reverberation.  Several  times  the  idea  has  been  suggested,1  and  in 
fact,  a  definite  system  has  actually  been  proposed,  whereby  various 
surfaces  of  different  coefficients  of  absorption  could  be  exposed.2 
None  of  these  systems,  however,  could  have  been  readily  adaptable 
to  the  kind  of  control  required  for  musical  purposes. 

The  realization  of  such  a  scheme,  of  course,  would  involve  not 
only  the  designing  of  appropriate  equipment  by  the  engineer,  but, 
as  well,  the  training  of  the  musician  so  that  he  might  understand  the 
full  possibilities  of  the  system.  The  latter  problem  is,  of  course,  not 
of  interest  to  us  here.  This  discussion  will  be  limited  to  the  musical 
requirements  from  an  engineering  standpoint.  It  must  be  noted  that 
in  many  cases  it  might  not  be  practicable  to  vary  the  time  of  rever- 
beration during  the  performance  of  a  piece  of  music ;  but  it  might 
even  then  be  practicable  to  vary  it  between  successive  pieces. 

In  general,  musical  compositions  may  be  very  roughly  divisible 
into  two  classes — solo  and  ensemble,  each  of  which  is  further  divisible 
into  slow  and  fast  music.  The  crudity  of  this  classification  is  ob- 
vious, but  it  is  at  least  indicative  of  the  range  of  types  of  music. 
It  is  rare  to  find  rapid,  brilliant  passages  for  one  instrument  in  or- 
chestral works  (with  the  possible  exception  of  solos  for  the  first 
violin) .  Music  is,  moreover,  characterized  partly  by  rhythm,  of  which 
the  elementary  component  is  the  beat.*  The  rapidity  or  slowness 
of  a  passage  depends  upon  the  lapse  of  time  between  beats.  Fig.  1 

*  The  word  "beat"  must  be  distinguished  from  the  common  acoustical  beat. 
As  here  used  it  has  the  more  common  musical  meaning,  indicating  the  instant 
of  beginning  a  certain  time  interval  in  music. 

122  PETER  CAPORALE  [j,  s.  M.  p.  E. 

shows  a  curve  indicating  the  duration  in  seconds,  between  beats 
produced  by  a  standard  metronome.  For  convenience  the  cor- 
responding musical  terms  are  also  given.  Now,  since  the  deleterious 
effect  of  reverberation  is  to  cause  overlapping  of  successive  sounds, 
the  problem  becomes  that  of  reducing  the  time  of  reverberation 
sufficiently  to  avoid  undesirable  overlapping.  But  it  must  be  re- 
membered that  not  in  all  cases  is  overlapping  to  be  completely 
avoided.  If  successive  sounds  pertain  to  the  same  harmony,  some 
overlapping  is  in  fact  desirable.  This,  however,  is  a  problem  for  the 
composer  rather  than  the  engineer. 

It  will  be  evident  from  Fig.  1  that,  besides  ease  of  control  (  a  special 
member  of  the  ensemble  may  be  assigned  to  the  control  box  with  its 
own  score),  rapidity  of  control  is  an  important  factor  in  the  design 
of  reverberation  control  equipment.  Another  determining  factor  is 
range  of  control;  and  finally,  the  control  must  be  silent  in  operation. 
These  factors  are  determined  by  musical  requirements.  There  are 
also  the  usual  factors  of  economy  of  installation,  operation,  and  main- 
tenance, which  determine  to  what  extent  the  other  requirements 
can  be  fulfilled. 

(A)  Ease  of  Control. — Several  reverberation  control  systems  have 
been  proposed  or  tried,1'2-3  all  of  .which  have  been  manually  operated 
devices.     A  notable  example  is  the  installation  of  the  National 
Broadcasting  Company  in  its  Chicago  studios.     It  is  quite  evident, 
however,  that  for  our  purpose  we  must  have  recourse  to  remote  con- 
trol, and  by  using  flexible  cables  the  control  box  might  be  one  of  the 
instruments  of  the  ensemble.     There  would  thus  be  a  musician  "play- 
ing the  auditorium,"  under  the  supervision  of  the  conductor.     For 
organs  this  would  mean  additional  buttons  for  its  already  complex 
control  panel. 

(B)  Rapidity  of  Control. — To  understand  the  problem  fully,  it 
will  be  necessary  to  consider  briefly  the  musical  forms  giving  rise  to 
it.     The  required  speed  is  a  function,  not  of  the  rapidity  of  the  music 
itself,  but  of  the  quickness  with  which  the  tempo  changes. 

As  has  already  been  indicated,  music  is  characterized  among  other 
things  by  rhythm,  and  a  composition  must  for  this  reason  be  divided 
into  beats,  which  are  grouped  into  larger  units  called  bars.  It  is 
the  latter  grouping  that  gives  to  a  passage  a  large  part  of  its  rhythmic 
character.  A  waltz,  for  example,  is  distinguished  by  having  three 
beats  to  a  bar,  etc.  But  also,  and  more  important  from  our  stand- 
point, the  bar  is  the  unit  to  be  considered  in  the  transition  from  a 

Feb.,  1933]  ACOUSTICS  OF  AUDITORIUMS  123 

slow  to  a  rapid  tempo  or  vice  versa;  that  is  to  say,  the  tempo  changes 
from  bar  to  bar  rather  than  from  beat  to  beat,  the  first  beat  of  a  bar 
coming  at  the  beginning  of  the  bar.  In  other  words,  the  tempo,  or  the 
rapidity  of  succession  of  beats,  does  not  usually  change  within  the  bar, 
but  between  bars.  For  example,  in  Fig.  2  (upper  chart)  which  is  a  sche- 
matic indication  of  a  sequence  of  bars,  each  having  three  beats  a,  b, 
and  c,  we  have  the  first  two  bars  marked  largo.  From  Fig.  1  we  see  that 
the  time  between  successive  beats  for  this  tempo  is  four  seconds,  and 
hence  the  length  of  each  bar  is  twelve  seconds.  The  third  and  fourth 
bars  being  marked  allegro,  the  time  between  beats  is  only  0.7  second, 
each  bar  representing,  therefore,  2.1  seconds,  or  less  than  one-fourth 
the  duration  of  each  of  the  first  two  bars.  Similarly  the  fifth  and  sixth 
bars  are  marked  andante,  with  1.2  seconds  between  beats  and  3.6 
seconds  to  each  bar.  Let  us  examine  the  conditions  such  a  sequence 
would  impose  on  a  reverberation  control  system. 

The  first  two  bars  (largo)  being  very  slow,  the  music  therein  con- 
tained depends  for  its  effect  on  largeness  of  tone*  rather  than  on 
rhythm.  The  time  of  reverberation  should  therefore  be  compara- 
tively long.**  Certainly  3  or  4  seconds  (usually  a  large  value  for  an 
auditorium  containing  an  audience)  would  not  be  too  long  for  these 
bars.  But  as  soon  as  we  get  to  bar  No.  3  (allegro)  the  bar  duration 
becomes  only  2.1  seconds,  and  the  period  of  reverberation  must  be 
reduced  to  prevent  the  successive  beats  from  overlapping.  Actually, 
whether  the  indicated  time  of  3  or  4  seconds  is  too  long  or  not,  is 
determined  by  the  music  itself.  For  the  case  referred  to,  this  time 
would  cause  two  successive  beats  to  overlap.  This  is  permissible 
and  even  desirable  in  those  cases  where  the  successive  beats  form 
part  of  the  same  "harmony."  In  other  cases,  the  time  would  natur- 
ally have  to  be  shorter.  The  time  mentioned,  however,  is  intended 
only  to  indicate  the  possible  range,  and  is  not  necessarily  correct 
for  all  music  marked  largo.  The  actual  value  must  be  determined  by 

*  Largeness  of  tone  is  concerned  mainly  with  amplitude  of  sound  as  opposed  to 
rhythm.  A  full  definition  would  involve  considerations  of  musical  tradition  and 
custom,  as  well  as  an  analysis  of  psychological  reaction  to  sound.  Largeness  of 
tone  involves  not  only  the  amplitude  of  the  sound,  but  the  wave-form  as  well. 
Thus,  we  hardly  speak  of  the  largeness  of  tone  of  the  oboe,  or  tympani,  or  cym- 
bals; but  we  do  speak  of  the  largeness  of  tone  of  a  cello  or  bass  viol,  or  of  the 
viola,  or  violin,  or  of  some  of  the  wind  instruments.  The  vernacular  of  music 
contains  many  terms  that  are  perfectly  clear  to  musicians,  but  yet  defy  simple 
and  concise  definition  for  the  layman. 

**  In  such  cases,  the  harmony  also  warrants  long  reverberation  time. 



[J.  S.  M.  P.  E. 

the  composer  who  has  been  taught  reverberation  control  and  its 
principles.  In  addition,  it  must  be  remembered  that  as  the  duration 
of  a  bar  decreases,  the  music  usually  depends  more  and  more  on 
rhythm  and  definition.  This  requires  a  still  shorter  reverberation 
time,  and  for  bars  No.  3  and  No.  4  its  value  will  have  to  be  of  the 
order  of  0.5  second  for  best  effects.  In  bars  No.  5  and  No.  6  we  are 
again  permitted  to  increase  the  reverberation  time,  but  in  this  case 
to  about  1.25  seconds  (the  optimum  in  all  cases  will  obviously  de- 
pend upon  the  nature  of  the  music  itself).  There  is  one  difference 
between  these  two  changes.  In  changing  from  bar  No.  2  to  bar  No.  3 
we  had  to  make  the  change  before  the  beginning  of  the  third  bar 

Bar  No. 


Time  Between  \ 

Oftfjf  c 

Duration  of 


b     c     a    b 

I  M  I  N  I  M  I  N  I  N  I  bl  & 

_    /*         J,  /^      _v.j_    27      .  _     2./     i^_    3.6         vl          3.5 J 

ifftf.  Sec  sec  sec.  sec        'p        Sec. 

U Largo n Allegro >< Andante M 


FIG.  2.  Above:  chart  showing  the  relation  between  the  intervals  between 
beats  and  the  duration  of  the  bar  for  different  tempos.  Below:  chart  indicating 
the  manner  of  changing  the  time  of  reverberation  when  the  tempo  is  changed. 

to  avoid  bad  effects  in  the  more  rapid  passage.  This  means  that  the 
end  of  bar  No.  2  must  be  borrowed  for  this  change,  and  if  the  change 
can  be  made  in  2  seconds  it  will  not  be  noticeable  (the  duration  of 
the  last  beat  of  bar  No.  2  being  4  seconds) .  In  changing  from  bar  No. 
4  to  bar  No.  5  we  should,  analogously,  borrow  time  from  bar  No.  5 
which  is  slower;  but  it  is  a  fact  that  most  music  is  so  arranged  that 
the  transition  from  a  rapid  to  a  slower  tempo  is  never  sudden, 
passing  through  a  rallentando  or  gradual  slowing  up.  Hence,  the 
conditions  imposed  by  this  change  are  never  severe,  time  being  avail- 
able from  both  bars.  Since  the  power  requirements  of  the  control 
system  are  determined  by  the  rapidity  of  the  control,  we  may  say 

Feb.,  1933] 



that  it  is  the  change  from  slower  to  more  rapid  tempo  that  is  the 
controlling  factor.  From  a  consideration  of  the  musical  literature  we 
may  state  that  the  time  of  change  from  maximum  to  minimum  rever- 
beration should  approach,  as  a  working  value,  one  second.  It  is 
evident  that  economic  considerations  will  determine  how  closely 
this  value  may  be  approached ;  a  slower  control  will  not  be  a  serious 
handicap  except  in  certain  special  musical  forms.  Fig.  2  (lower  chart) 
shows  the  same  sequence  of  bars  of  Fig.  2,  with  the  reverberation  time 
indicated,  and  a  possible  way  of  indicating  the  interval  over  which 
the  change  may  be  effected. 

(C)     Range  of  Control  and  Silence  of  Operation. — This  is  a  subject 
that  always  arouses  comments  due  to  the  contradictory  require- 

.3  .4-  .f  .6 

Volume  of  Room  in  Million  Cx   Ft. 

FIG.  3.  Approximate  relation  between  size  of  orchestra  and  vol- 
ume of  auditorium  (from  information  given  in  Circular  300,  U.  S. 
Bureau  of  Standards,  1926). 4 

ments  of  large  tone  and  good  articulation.  The  writer's  experience 
with  outdoor  concerts,  however,  has  shown  beyond  a  doubt  that 
maximum  absorption  is  most  desirable  for  passages  requiring  good 
articulation.  In  general  such  passages  do  not  require  large  tone  but 
only  crispness  and  brilliance.  The  ill  effects  of  open-air  theaters  are 
evident  only  in  slow  movements  where  the  chief  emotional  medium  is 
tone.  For  a  given  size  of  auditorium  the  maximum  value  of  rever- 
beration time  will  be  limited  by  the  audience,  the  orchestra  personnel, 
and  the  wall  surfaces;  similarly,  the  minimum  value  will  be  limited 
by  the  maximum  obtainable  absorption  in  the  given  volume,  though 
this  lower  limit  is  less  definite  than  the  upper  limit.  These  limits 
prevent  the  same  absolute  range  of  control  from  being  applicable 

126  PETER  CAPORALE  [j.  s.  M.  P.  E. 

in  all  cases.  However  the  control  equipment  should  be  calibrated  in 
time  units  for  uniformity  and  to  minimize  troubles  in  scoring. 
Most  concert  halls  designed  for  the  same  size  of  orchestra  should  have 
similar  characteristics ;  hence,  the  above-mentioned  limitations  imply 
simply  that  the  scoring  for  the  control  should  depend  on  the  size 
of  orchestra,  just  as  at  present  there  are  different  arrangements  of  the 
same  composition  for  different  sizes  of  ensembles.  For  convenience 
the  approximate  relation  between  the  size  of  orchestra  and  the 
volume  of  the  auditorium  is  shown  in  Fig.  3.4 

One  thing  is  to  be  pointed  out  relative  to  this  use  of  reverberation 
control.  It  is  the  use  of  absorbents  having  approximately  flat  fre- 
quency characteristics.  In  other  words,  if  a  control  key  represent  a 
reverberation  time  of  T\t  say,  for  the  notes  of  a  piccolo,  it  must 
represent  the  same  time*  for  the  notes  of  a  bass  tuba  or  a  bass  viol. 
If  this  is  not  the  case,  it  is  possible  to  score  correctly  provided  the 
actual  frequency  characteristic  is  known,  but  this  introduces  undesir- 
able complications,  inasmuch  as  two  halls  possessing  different 
frequency  characteristics  would  require  separate  scoring. 

The  silent  operation  of  the  equipment  is,  of  course,  necessary  to 
avoid  disturbing  or  distracting  factors  during  the  rendition,  and  is  an 
end  to  be  attained  through  the  proper  mechanical  design  of  the 
system  and  the  proper  sound-proofing  of  the  prime  movers. 

Use  of  Reverberation  Control  for  Solo  Work. — It  has  already  been 
pointed  out  that,  except  for  organs,  the  instantaneous  control  of 
reverberation  by  instrumental  soloists  is  impracticable.  The  best 
that  can  be  done  in  such  cases  is  to  provide  the  best  average  reverbera- 
tion time  for  the  given  composition;  this  is  a  problem  for  the  musi- 
cian, not  the  engineer.  It  is  interesting  to  the  latter  to  know,  how- 
ever, that  having  met  the  requirements  already  outlined,  he  will  have 
covered  the  requirements  for  solo  work  which,  therefore,  does  not 
require  his  special  attention. 

*  Note  that  this  does  not  refer  in  the  least  to  the  desirable  characteristic  of  an 
auditorium  having  no  reverberation  control.  Several  investigators  have  al- 
ready studied  this  problem.  What  is  referred  to  here  is  the  fact  that  a  given  key 
or  switch  on  the  reverberation  control  box  must,  if  it  is  marked  T\,  produce  that 
reverberation  time  under  any  circumstance.  If  then,  it  is  desirable  to  have  a 
reverberation  time,  T\,  for  the  bass  viol,  and  a  time,  T2,  for  the  piccolo  (other  condi- 
tions being  equal)  then,  that  means  that  T2  should  be  called  for  when  the  piccolo 
is  playing  and  T\  when  the  bass  viol  is  playing.  The  case  of  ensemble  is  more 
complex,  and  as  to  what  is  the  optimum  time  for  a  given  passage  involving  cer- 
tain given  instruments  is  a  problem  to  be  analyzed  separately. 

Feb.,  1933]  ACOUSTICS  OF  AUDITORIUMS  127 

Conclusions. — To  sum  up  the  basic  requirements  for  a  reverbera- 
tion control  system  for  the  continuous  control  of  auditorium  acoustics 
from  a  musical  standpoint,  we  have: 

(a)  Ease  of  operation. 

(b)  The  time  required    to    pass    from  maximum  to  minimum 
reverberation  should  approach  one  second;    a  value  less  than  this 
would  impose  too  severe  economic  requirements. 

(c)  The  range  of  control  should  be  a  maximum,  and  be  covered 
by  steps,  the  number  of  which  should  be  experimentally  determined. 

(d)  The  operation  of  the  equipment  must  produce  no  disturbing 
or  distracting  noises. 


1  KNUDSEN,  V.:     "Architectural  Acoustics,"  John  Wiley  &  Sons,  New  York, 
1932,  p.  413. 

2  PETZOLD,  ERNEST:     "Regulation  of  Acoustics  of  Large  Rooms,"  /.  Acoustical 
Soc.  ofAmer.,  HI  (Oct.,  1931),  No.  2,  p.  288. 

3  EBERT,  SYLVANUS  J.:     "Design  and  Acoustics  of  Broadcast  Studios,"  Radio 
Engineering  (Jan.,  1932),  p.  13. 

4  HEYL,  P.  R. :     "Architectural  Acoustics,"  U.  S.  Bureau  of  Standards,  Circular 
300,  1926. 


C.    R.    DAILY** 

Summary. — A  description  is  presented  of  a  complete  new  Western  Electric  double 
film  portable  recording  system  recently  perfected  by  Electrical  Research  Products, 
Inc.  The  equipment  is  mounted  in  a  trunk  and  is  designed  to  be  used  for  location, 
industrial,  and  educational  recording  where  portability  is  of  the  utmost  importance. 
Entirely  new  designs  of  the  system  amplifier,  noise  reduction  unit,  d-c.  interlocking 
motor  system,  double  film  recorder,  and  other  units  liave  been  perfected.  The  im- 
proved moving  coil  microphone,  permanent  magnet  light  valve,  and  many  other 
recent  equipment  developments  have  been  used.  The  minimum  weight  of  the  simplest 
sound  recording  channel  of  this  new  type  is  approximately  325  pounds.  By  adding 
other  units,  sound  recording  systems  of  any  degree  of  elaborateness  may  be  established. 

Portability  and  reliability  of  picture  and  sound  equipment  de- 
termine the  limitations  of  the  talking  picture  screen.  While  the 
field  of  action  of  the  motion  picture  camera  is  practically  unlimited, 
its  usefulness  has  been  materially  enhanced  by  the  development  of 
highly  portable  sound  equipment.  The  first  sound  recording  chan- 
nels used  on  location  consisted  of  apparatus  of  the  fixed-channel 
type  remounted  and  placed  on  trucks.  Such  channels,  while  very 
useful,  clearly  demonstrated  the  need  of  still  lighter  and  more  port- 
able equipment.  Later  came  the  channel  consisting  of  individual 
units  mounted  in  trunks,  which  could  be  used  on  locations  not 
accessible  to  the  sound  truck.  The  latter  form  of  equipment  has 
proved  to  be  more  generally  useful  and  for  that  reason  has  been 
more  intensively  developed  than  any  other. 

This  paper  presents  a  description  of  a  new  double  film  trunk 
channel  for  recording  which,  on  account  of  its  light  weight  and  ease 
of  operation,  overcomes  the  many  objections  found  in  earlier  designs 
and  fills  a  very  definite  need  on  the  part  of  the  studios  and  others 
who  have  need  of  portable  sound  recording  facilities  of  the  most 
advanced  design  and  highest  order  of  flexibility. 

*  Received  November  30,  1932. 

**  Electrical  Research  Products,  Inc.,  New  York,  N.  Y. 


Some  of  the  new  developments  that  have  made  possible  the 
design  of  this  improved  channel  are  as  follows:  The  moving  coil 
microphone  is  lighter,  more  sensitive,  and  less  subject  to  adverse 
weather  conditions  than  the  condenser  type  of  transmitter.  The 
permanent  magnet  light  valve  and  modulator  unit  are  much  smaller 
and  more  sensitive  than  the  light  valve  assemblies  formerly  used,  and 
have  made  possible  a  much  lighter  and  more  compact  amplifier 
and  battery  assembly.  The  entirely  new  d-c.  interlocking  motor 
system  requires  a  minimum  of  power  to  operate,  and  provides 
reliable  speed  control  for  all  cameras  and  recorders.  New  and 
lighter  transformers  have  reduced  the  weight  of  the  speech  system, 
while  new  vacuum  tubes  have  increased  the  carrying  capacity  and 
reliability  of  operation  of  the  amplifiers,  at  the  same  time  allowing 
for  a  considerable  reduction  in  both  A-  and  5-battery  consumption. 
Improvements  made  in  the  noise  reduction  amplifier  and  control 
unit  materially  reduce  the  weight  of  this  part  of  the  equipment. 


A  strong,  but  light,  welded  duralumin  case  is  used  to  contain  this 
new  trunk  channel,  each  complete  case  weighing  less  than  90  pounds. 
Specially  impregnated  insulation  has  been  used  in  the  wiring  to 
prevent  deterioration  in  warm,  humid  climates.  Considerable 
care  has  been  taken  to  reduce  the  number  of  connections  and  simplify 
the  control,  and  yet  assure  ease  of  set-up  and  reliability  of  operation 
in  the  field. 

A  complete  sound  recording  channel  consists  of  four  distinct 
groups  of  equipment:  sound  pick-up  devices,  amplifiers,  film  re- 
corders, and  motors,  with  their  associated  sources  of  power.  The 
details  of  design  of  each  of  these  units  have  been  carefully  studied 
and  the  operation  of  the  assembly  of  units  considered  as  a  whole  so 
that  a  unified  system  could  be  provided. 

The  following  tabulation  lists  the  various  units  that  have  been 
designed  for  these  recording  channels.  Several  groupings  of  equip- 
ment are  mentioned  in  order  to  illustrate  the  flexibility  of  the  channel 
in  building  up  systems  to  meet  varying  recording  needs: 

1.     Pick-Up  Devices 

(a)  One  or  two  moving  coil  transmitters  connected  directly  to  the  main 
amplifier.  Either  transmitter  may  be  used  at  a  time.  No  external 
transmitter  amplifiers  required. 

130  C.  R.  DAILY  [j.  s.  M.  P.  E. 

(b)  One   or   more   moving  coil   transmitters   or   condenser   transmitters 
with   single-  or   two-stage   transmitter   amplifiers    connected   to   an 
extension   3-dial    mixer   and    volume    control    cabinet.     This  mixer 
connects  by  cable  to  the  main  amplifier. 

2.  Amplifiers 

(a)  The  main  amplifier  provides  in  one  cabinet  all  the  gain  required  for 
the  operation  of  this  channel  with  a  single  moving  coil  microphone 

(&)  The  same  amplifier  is  also  used  with  the  extension  mixer  mentioned 
above  for  multi-microphone  pick-up  and  mixing. 

(c)  The  noise  reduction  amplifier  and  control  unit  derives  its  input  from 
the  film  recorder  and  may  be  used  if  desired. 

3.  Film  Recorders 

(a)  A  new  film  recorder  using  the  permanent  magnet  light  valve  and 
carrying  the  necessary  lamp  controls  and  motor  switches  is  available 
for  the  double  film  channel.  Split  beam  photoelectric  cell  monitor 
is  available  with  this  recorder. 

4.  Power  Supply 

Three  fundamental  motor  systems  are  available  for  use  with  this  channel : 

(a)  Standard  interlocking  motors  to  be  used  with  the  present  distributor 

(&)  A  new  type  of  double  wound  d-c.  interlocking  motors  with  manual 
speed  control.  Speed  may  be  controlled  automatically  by  adding  a 
special  control  cabinet  and  a  generator-distributor  case.  A  maxi- 
mum of  three  picture  cameras  and  the  film  recorder  may  be  used 
with  this  system.  Twelve- volt  storage  batteries  are  the  only  source 
of  power  required. 

(c)  Synchronous  induction  motors  operating  from  a  50-  or  60-cycle,  3- 
phase,  220-volt  power  supply. 

Fig.  1  shows  the  simplest  arrangement  of  the  double  film  recording 
system.  A  moving  coil  microphone,  amplifier,  film  recorder,  camera, 
two  motor  switch  boxes,  three  12-volt  battery  boxes,  and  the  necessary 
cables  make  up  the  entire  channel.  The  speed  of  the  interlocking 
double  wound  d-c.  motors  is  manually  controlled.  The  sound 
equipment  by  itself  weighs  approximately  325  pounds,  and  the 
picture  camera  and  its  tripod,  motor,  battery,  and  cable,  170  pounds, 
making  a  total  of  495  pounds.  Additional  cameras  may  be  used 
with  this  set-up  if  desired. 

Fig.  2  shows  a  more  elaborate  double  film  recording  channel 
having  an  extension  mixer  for  three-microphone  pick-up  and  mixing, 
order  wire,  photoelectric  cell  monitor,  and  provision  for  automatic 
speed  control  of  the  motor  system  of  the  film  recorder  and  one  or 

Feb.,  1933] 



more  cameras.  This  form  of  the  channel  would  be  satisfactory  for 
heavy  duty  location  work  with  a  large  company.  The  speech 
equipment  and  motor  system  complete  weigh  approximately  850 
pounds,  while  the  cameras  and  their  auxiliary  equipment  weigh, 
as  mentioned  before,  about  170  pounds  each.  This  channel  is 
shown  in  schematic  form  in  Fig.  3.  As  each  case  weighs  less  than 
90  pounds  when  ready  for  shipment,  even  this  elaborate  system 
may  be  quickly  packed  on  a  truck  and  taken  on  location.  The 

FIG.  1.     Minimum  complete  double  film  recording  system. 

entire  system  may  be  unpacked  and  made  ready  for  operation  in 
less  than  ten  minutes  by  two  or  three  men. 

Other  arrangements  of  the  equipment  are  possible,  those  just 
described  being  shown  as  examples  of  the  flexibility  of  operation  of 
the  system.  Thus,  wide-range  film  recording  is  effected  by  adding 
the  necessary  units  of  equipment  to  the  system  by  means  of  jacks 
provided  in  the  portable  trunk  units.  All  plug  and  jack  connections 
are  clearly  marked  to  facilitate  setting  up  the  equipment  in  the  field. 


C.  R.  DAILY 

[J.  S.  M.  P.  E. 

A  brief  description  will  now  be  given  of  each  of  the  component 
parts  of  this  system. 


The  amplifier  used  with  this  channel  is  entirely  new  in  design  and 
construction,  and  has  a  minimum  weight  and  power  consumption. 
Fig.  4  shows  a  front  view  of  the  case,  which  is  12  inches  deep  and  has 
a  front  panel  19  inches  wide  by  12  inches  high.  It  weighs  80  pounds 

FIG.  2.     Double  film  recording  system  with  extension  mixer,  noise  reduction, 
photoelectric  cell  monitor,  order  wire,  and  automatic  speed  control. 

complete  with  B  and  C  batteries.  The  shape  of  this  case  has  been 
made  standard  for  practically  all  units  of  the  channel  so  as  to  facilitate 
stacking  of  equipment.  Fig.  5  shows  the  internal  construction  of 
the  amplifier. 

The  speech  input  to  the  amplifier  is  normally  taken  from  the 
output  of  one  of  the  new  moving  coil  microphones,1  obviating  the 
necessity  of  using  a  separate  transmitter  amplifier  and  polarizing 
battery.  This  type  of  transmitter  may  be  used  in  humid  climates 
and  requires  no  special  precautions  such  as  were  required  with  the 

Feb.,  1933] 



condenser  type.  This  feature  should  appeal  to  the  sound  man  who 
is  required  to  go  to  locations  having  difficult  climatic  conditions. 

The  maximum  gain  of  the  amplifier  is  approximately  104  db., 
which  is  sufficient  to  modulate  fully  a  permanent  magnet  light  valve 
used  for  recording  speech  out-of-doors  at  distances  of  15  feet  to 
30  feet  from  the  moving  coil  transmitter.  A  volume  indicator  and 
headphones  are  provided  for  monitoring. 

The  block  of  B  batteries  mounted  in  the  main  amplifier  will 
operate  this  amplifier  for  fifteen  to  twenty  hours,  after  which  it  can 
be  easily  replaced.  This  battery  life  is  sufficient  for  several  days' 

FIG.  3.     Schematic  diagram  of  double  film  recording  system. 

operation.  The  filament  supply  is  obtained  from  the  exciting  lamp 
storage  battery.  A  very  desirable  feature  of  the  system  is  the  fact 
that  the  amplifier  may  be  located  as  far  as  400  feet  from  the  recorder 
and  its  associated  12- volt  lamp  battery,  as  a  voltage  of  only  4.5  is 
required  at  the  filament  terminals.  It  is  also  possible  to  use  a  cable 
between  the  moving  coil  transmitter  and  the  amplifier  100  feet  to 
300  feet  long,  so  that  a  very  wide  field  of  operation  may  be  covered. 
A  special  jack  is  provided  for  local  external  A  and  B  batteries, 
providing  for  the  use  of  heavier  duty  B  batteries  when  operating  on 
locations  where  extreme  portability  is  not  required.  A  special 
external  5-battery  box  for  the  main  amplifier  and  extension  mixer 


C.  R.  DAILY 

[J.  S.  M.  P.  E. 

is  available,  providing  for  two  sets  of  135-volt  batteries  having  a 
useful  life  in  excess  of  100  hours. 

The  Western  Electric  264-^4  vacuum  tube  is  used  for  all  speech 
transmission  services  in  the  system,  thereby  reducing  the  number 
and  types  of  tubes  that  would  normally  be  carried.  Eight  of  these 
tubes  are  used  in  the  main  amplifier,  the  total  filament  current  of 
which  is  only  0.9  ampere  at  4.5  volts,  the  total  plate  current  being 
only  12  milliamperes  at  135  volts.  These  values  of  filament  and 
plate  current  represent  a  considerable  reduction  from  those  found 
in  earlier  systems,  and  will  assist  particularly  on  expeditions  where 
every  pound  of  weight  must  be  considered.  A  separate  B  battery 
is  not  required  for  the  internally  mounted  transmitter  amplifier; 

FIG.  4.    Portable  system  amplifier,  front  view. 

this  omission  effects  a  considerable  saving  in  weight  and  maintenance. 

Provision  has  been  made  for  directly  reading  the  filament  voltage 
and  plate  current  of  each  tube.  A  jack  and  key  are  mounted  on  the 
amplifier  so  that  external  high-  or  low-pass  filters  or  equipment  for 
wide-range  recording  may  be  connected  in  the  circuit  if  needed.  A 
speech  equalizer  is  mounted  in  the  main  amplifier  and  can  be  con- 
nected to  the  circuit  by  a  key.  An  order  wire  sub-set  has  been 
mounted  in  the  amplifier  so  that  the  recordist  and  extension  mixer 
may  communicate  with  each  other. 

If  pick-up  from  more  than  one  microphone  is  required,  a  simple 
switching  arrangement  allows  for  the  alternative  use  of  either  of 
two  moving  coil  microphones.  If  mixing  facilities  are  required 

Feb.,  1933]  NEW  SOUND  RECORDING  SYSTEM  135 

for  several  microphones,   an  extension  mixer  case  is  used,  which 
connects  directly  to  the  main  amplifier  by  means  of  two  cables. 


The  extension  mixer  case  is  designed  to  operate  from  the  output 
of  one,  two,  or  three  single-  or  two-stage  transmitter  amplifiers 
using  either  condenser  or  moving  coil  microphones.  Three  mixer 
dials,  a  single-stage  booster  amplifier,  a  volume  control  potentiometer, 
a  filter  jack,  a  volume  indicator,  a  headphone  monitor  extension, 
and  an  order  wire  are  provided.  The  A  -battery  supply  is  provided 
by  the  lamp  battery,  while  the  required  B- voltage  is  supplied  from  a 
separate  battery  box  connected  at  the  main  amplifier. 


The  value  of  noise  reduction  has  been  clearly  demonstrated  during 
the  past  year.  The  standard  studio  type  of  equipment  was  de- 

FIG.  5.    Portable  system  amplifier,  interior  view. 

scribed  before  the  Society  of  Motion  Picture  Engineers  in  October, 
193 1.2  An  entirely  new  design  for  noise  reduction  equipment,  how- 
ever, has  been  worked  out  for  this  portable  channel.  The  principal 
object  in  designing  a  new  noise  reduction  circuit  for  location  service 
was  to  reduce  materially  the  weight  of  this  important  piece  of  equip- 
ment. A  gross  weight  of  only  68  pounds,  including  tubes  and  B 
and  C  batteries,  has  been  achieved  with  no  sacrifice  in  quality. 
Filament  power  is  obtained  from  the  12- volt  lamp  battery,  only 
0.6  ampere  being  required.  The  total  plate  circuit  drain  is  ap- 
proximately 18  milliamperes  under  normal  operating  conditions, 
and  is  provided  by  a  135- volt  block  of  B  batteries  mounted  within 
the  case.  One  block  of  these  batteries  will  operate  the  unit  for  ten 
to  fifteen  hours.  These  blocks  of  B  batteries  are  interchangeable 


C.  R.  DAILY 

[J.  S.  M.  P.  E. 

with  those  used  in  the  main  amplifier,  and  may  be  replaced  as  a  unit 
in  a  few  minutes.  External  B  batteries  may  be  used  if  desired. 
The  filament  voltage,  plate  current  of  each  tube,  and  light  valve 
bias  current  can  be  read  directly. 

Both  the  noise  reduction  amplifier  and  light  valve  control  unit 
have  been  mounted  in  one  case,  and  have  been  so  arranged  that  the 
necessary  adjustments  may  be  made  very  quickly,  thereby  facili- 

FIG.  6.    Film  recorder. 

tating  the  line-up  of  the  channel  for  operation  in  the  field,  particu- 
larly in  cases  where  it  is  necessary  to  get  into  action  in  a  very  short 

A  1000-cycle  oscillator  is  mounted  within  the  noise  reduction 
case,  and  is  used  to  adjust  the  noise  reduction  unit  for  cancellation 
of  the  bias  current  and  to  determine  the  overload  point  of  the  light 
valve.  The  oscillator  also  provides  a  useful  source  of  tone  for 
general  testing  purposes. 

Feb.,  1933] 




An  entirely  new  design  of  film  recorder  is  used  in  this  channel. 
A  front  view  of  the  recorder  with  the  door  of  the  camera  and  modu- 
lator unit  open  is  shown  in  Fig.  6.  The  mechanism  is  mounted  in  a 
casting  not  much  larger  than  a  standard  motion  picture  camera  and 
is  placed  on  top  of  the  duralumin  base  which  contains  the  necessary 
controls  for  the  recording  lamp,  light  valve,  photoelectric  cell  moni- 
toring apparatus,  order  wire  sub-set  equipment,  and  switches  for 
the  motor  system.  The  camera  has  been  designed  so  that  the  door 
can  not  be  closed  if  any  of  the  guide  or  tension  rollers  are  not  in 
their  proper  positions. 

A  new  permanent  magnet  light  valve,  recently  perfected  by  the 
Bell  Telephone  Laboratories,  is  used  in  this  recorder.  Its  use  makes 

FIG.  7.     Photoelectric  cell  monitor  and  storage  case. 

possible  a  considerable  reduction  in  the  size  and  weight  of  the  re- 
corder, and  since  it  is  more  sensitive  than  the  standard  studio  type 
of  light  valve,  it  is  possible  to  reduce  materially  the  battery  drain 
of  the  main  amplifier  by  using  output  tubes  of  lower  current  ca- 
pacity than  formerly. 

The  sprocket  that  pulls  the  film  past  the  modulated  light  beam 
has  been  carefully  filtered.  An  aperture  of  the  roller  gate  type  is 
used,  and  has  proved  to  be  very  satisfactory.  This  aperture  was 
first  used  in  the  Western  Electric  studio  reproducing  machine,3 
and  possesses  many  advantages  over  the  sliding  gate  formerly  used. 
A  tension  roller  also  helps  to  assure  evenness  of  motion  of  the  film 
past  the  light  gate. 

Photoelectric  cell  monitoring  may  be  used  if  desired,  since  a 
deflecting  mirror  is  mounted  in  the  modulator  so  that  the  modulated 

138  C.  R.  DAILY  [j.  s.  M.  p.  E. 

light  that  does  not  fall  upon  the  objective  lens  is  reflected  to  a  caesium 
oxide  photoelectric  cell.  The  output  of  this  cell  is  connected  to  a 
single-stage  amplifier  and  a  pair  of  headphones.  The  output  trans- 
former and  90-volt  B  battery  for  this  amplifier  are  mounted  in  an 
auxiliary  case,  shown  in  Fig.  7.  This  auxiliary  case  connects  to 
the  recorder  by  a  short  cable,  and  is  used  also  for  storage  of  some  of 
the  motor  control  units,  headsets,  handsets,  spare  light  valves, 
microscopes,  tubes,  etc. 

The  output  of  the  photoelectric  cell  amplifier  or  the  direct  monitor 

FIG.  8.     Motor  control  cabinet  and  speed  control  motor. 

may  be  patched  to  an  auxiliary  amplifier  to  provide  loud  speaker 
monitoring  facilities  if  desired. 


Standard  interlocking,  synchronous,  or  the  new  double  wound 
interlocking  d-c.  motors  may  be  used  with  this  sound  recording 
system.  The  following  section  outlines  the  general  operating  features 
of  each  of  these  motor  systems. 

D-C.  Interlocking  Motors. — A  new  design  for  the  d-c.  interlocking 
of  motors  has  been  perfected.  The  3-phase  winding  on  the  armature 
and  a  special  type  of  field  construction  eliminate  hunting  and  over- 
come the  irregularity  formerly  experienced  with  this  type  of  motor 

Feb.,  1933] 



system.  Interlocking  action  between  these  motors  is  very  positive, 
but  is  so  designed  that  it  is  impossible  to  burn  out  the  armature  or 
cause  destructive  arcing  of  the  commutator  due  to  an  out-of-phase 
condition  when  starting  or  throwing  additional  motors  on  the  line. 
A  single  12- volt  storage  battery  is  the  only  source  of  power  required 
for  each  motor.  By  proper  design,  the  danger  of  burning  the  com- 
mutator at  this  low  voltage  has  been  eliminated  and  very  reliable 
operation  of  the  motors  obtained. 

With  the   double  film  system   and  manual   speed   control,   one 
battery  is  used  for  the  amplifier,  one  for  the  recorder  motor,  and 

FIG.  9.     Cases  for  12-volt  batteries. 

one  for  each  camera  that  may  be  required.     Thus,  the  power  system 
can  be  readily  expanded  to  meet  production  requirements. 

A  small  switch  box  containing  a  field  rheostat,  relay,  and  three- 
position  switch  is  associated  with  each  motor.  If  the  switch  is 
thrown  to  the  "non-synchronous"  position  each  motor  may  be  run 
independently  of  the  others.  This  arrangement  permits  the  taking 
of  silent  shots  at  any  speed  and  for  the  photographing  of  numbering 
slates.  If  the  switch  is  operated  to  the  "interlock"  position,  all 
motors  in  the  system  may  be  started  simultaneously  from  any  one 
motor.  An  "off"  position  is  also  provided  so  that  any  motor  may 
be  readily  disconnected  from  the  line. 

140  C.  R.  DAILY  [j.  s.  M.  P.  E. 

Three  methods  of  speed  control  are  available  for  use  with  the 
double  wound  d-c.  interlock  system.  The  simplest  is  manual  control 
of  all  motors  by  the  recordist,  who  adjusts  and  maintains  the  speed 
of  the  system  by  means  of  a  rheostat  while  observing  a  tachometer 
mounted  on  the  recorder. 

Automatic  speed  control  using  the  same  d-c.  motors  may  be 
obtained  by  adding  a  special  control  cabinet  and  speed  control 
motor.  These  units  are  mounted  in  separate  cases  weighing  about 
55  and  70  pounds,  respectively,  and  are  shown  in  Fig.  8.  A  12-volt 
storage  battery  for  each  unit  is  required  to  operate  this  system,  and 
the  speed  control  is  equivalent  to  that  obtained  with  the  permanent 
channel  distributor  system  installations. 

Another  method  of  using  these  d-c.  motors  is  to  connect  the  inter- 
lock windings  to  a  public  service  company's  3-phase,  220-volt  line 
to  provide  interlock  while  the  power  to  drive  the  motor  is  still  pro- 
vided by  12-volt  batteries.  Thus  synchronous  operation  is  obtained 
and  the  speed  control  is  quite  satisfactory. 

Synchronous  Motors. — A  second  type  of  motor  system  involves 
the  use  of  3-phase  induction  synchronous  motors  designed  to 
operate  from  a  220-volt  supply.  For  portable  use  this  supply  may 
be  derived  from  either  the  public  service  lines  or  from  a  portable 
d-c.  to  a-c.  motor-generator  set  which  is  available.  The  d-c.  motor 
of  the  generator-set  operates  from  a  36-volt  battery  comprised  of 
three  standard  12-volt  batteries  connected  in  series,  the  generator 
delivering  3-phase  power  at  220  volts.  With  this  method  of  drive 
the  motor  speed  is  a  direct  function  of  the  speed  of  the  motor-gen- 
erator set  which  is  controlled  manually. 

Standard  Interlock  Motors. — In  existing  fixed  channels  a  motor 
system  of  the  interlocking  type  has  been  supplied,  which  can  also 
be  used  to  drive  the  recorder  and  cameras  of  the  portable  channel. 
Standard  interlocking  motors  with  special  adapters  have  been  built 
so  that  they  may  be  connected  directly  to  existing  studio  motor 
lines  and  distributors. 

With  the  three  motor  systems  that  are  available  it  is  possible  to 
meet  any  field  recording  condition.  The  primary  power  may  be 
either  12-volt  d-c.  or  3-phase,  220-volt  a-c.  The  alternating 
current  may  be  generated  either  locally  or  taken  from  a  220-volt 
supply  line.  Speed  control  may  be  either  manual  or  automatic, 
depending  upon  the  requirement  of  the  material  that  it  is  desired 
to  record. 

Feb.,  1933]  NEW  SOUND  RECORDING  SYSTEM  141 


Consideration  was  given  to  the  idea  of  using  135-volt,  heavy  duty 
B  batteries  to  drive  the  motors  when  used  on  location,  but  it  was 
found  that  48  pounds  of  these  batteries  would  not  have  sufficient 
power  to  pull  more  than  6000  feet  of  film  through  the  recorder. 
Therefore,  the  replacement  and  expense  of  this  type  of  battery  would 
be  a  major  problem  on  an  expedition.  The  decision  to  use  single 
storage  batteries  of  the  12- volt,  36-pound  airplane  type  for  each 
motor  materially  simplifies  the  field  requirements  and  provides  at 
the  same  time  sufficient  power  to  run  over  8000  feet  of  film  without 
recharging.  This  battery  life  corresponds  to  at  least  two  days  of 
normal  operation  on  location.  The  batteries  are  mounted  in  a 
duralumin  carrying  case  equipped  with  a  connecting  cable  and  jack. 
The  weight  per  unit  is  only  51  pounds.  A  view  of  one  of  these 
battery  cases  is  shown  in  Fig.  9.  The  same  type  of  battery  is  used 
for  all  services  in  the  channel,  such  as  lamp  and  amplifier  filament 
current  supply.  A  heavier  duty  battery  of  the  same  type  is  also 
available.  A  compact  gasoline  motor  and  direct  coupled  d-c. 
generator  weighing  approximately  120  pounds  is  available  for 
battery  charging  and  will  enable  the  d-c.  interlocking  system  to 
operate  continuously  in  the  field  without  requiring  replacement  of 

In  conclusion,  it  can  be  stated  that  there  has  been  made  available 
an  entirely  new  group  of  sound  recording  units  that  are  capable  of 
meeting  practically  any  requirement  imposed  on  a  double  film 
recording  system.  The  various  assemblies  are  light  in  weight  and 
are  of  such  rugged  construction  that  they  may  be  readily  transported 
to  any  desired  location.  The  quality  of  recording  obtained  with  the 
equipment  is  equivalent  to  that  obtained  with  the  best  fixed  channel 
installations  now  in  service. 


1  JONES,  W.  C.,  AND  GILES,  L.  W.:    "A  Moving  Coil  Microphone  for  High 
Quality  Sound  Reproduction,"  /.  Soc.  Mot.  Pict.  Eng.,  XVII  (Dec.,  1931),  No.  6, 
p.  977. 

2  SILENT,  H.  C.,  AND  FRAYNE,  J.  G.:   "Western  Electric  Noiseless  Recording," 
/.  Soc.  Mot.  Pict.  Eng.,  XVIII  (May,  1932),  No.  5,  p.  551. 

3  KUHN,  J.  J.:    "A  Sound  Film  Re-recording  Machine,"  /.  Soc.  Mot.  Pict. 
Eng.,  XVII  (Sept.,  1931),  No.  3,  p.  326. 



The  following  material  dealing  with  the  principles  relating  to  the  control  of  the 
effectiveness  of  graphical  presentation  of  engineering  data  is  abstracted  from  the 
American  Recommended  Practice  on  the  subject  which  was  approved  by  the  Ameri- 
can Standards  Association  on  Nov.  11,  1932  (ASA  Z15.1 — 1932).  The  standard 
prepared  by  a  sub-group  of  the  sub-committee  on  Engineering  and  Scientific 
Graphs  of  the  Sectional  Committee  on  Graphical  Presentation,  under  the  procedure 
of  the  American  Standards  Association,  29  W.  39th  St.,  New  York,  N.  Y.  The 
American  Society  of  Mechanical  Engineers  took  the  official  leadership  in  the  devel- 
opment of  this  project.  The  original  draft  was  presented  before  the  American 
Society  of  Mechanical  Engineers  in  December,  1931. 

The  recommended  practices  given  below  relate  to  engineering  and 
scientific  charts  prepared  for  use  as  lantern  slides.  Although  cer- 
tain general  principles  apply  to  the  entire  field  of  graphics,  including 
time-series  charts,  computation  charts,  illustrative  diagrams,  etc.,  no 
attempt  is  made  here  to  cover  such  a  broad  field.  Instead,  atten- 
tion has  been  directed  chiefly  to  general*'1  and  specific  suggestions 
applying  to  the  most  common  variety  of  engineering  and  scientific 
charts — line  charts  that  show  the  relation  between  two  variable 

Charts  made  in  accordance  with  these  recommendations  are  suit- 
able for  use  as  lantern  slides,  when  reduced  to  one-third  their  original 
dimensions.  With  slight  modifications  as  to  line  widths,2  these 
recommendations  are  also  usually  applicable  to  charts  prepared  for 
use  both  as  lantern  slides  and  as  illustrations  for  publication. 


(1)  An  engineering  or  scientific  chart  shown  on  a  lantern  slide 
is  only  an  illustration,  presupposes  explanation  by  the  speaker,  and 
usually  can  not  be  complete  in  itself. 

(2)  It  should  present  one  central  idea,  and  should  be  free  from 
all  lettering  and  lines  that  are  not  essential  to  a  clear  understand- 
ing of  its  message.     The  number  of  words  on  the  chart  should  be 
held  to  a  minimum  (a  useful  rule  is  to  aim  at  a  total  of  not  more  than 
15  words,  or  not  more  than  20  words  if  there  is  a  title). 

(3)  Supplementary  data  or  formulas  should  not  be  shown  unless 

*  For  reference  notes  see  pages  148  and  149. 



absolutely  necessary,  in  which  case  they  should  be  isolated  in  posi- 
tion and  enclosed  by  a  light  line  border. 

(4)  Proportions  of  about  7  by  10  are  suggested3  for  the  over-all 
dimensions  of  lantern  slide  charts.     In  choosing  between  a  vertical 
and  a  horizontal  rectangle,  consider  which  one  presents  the  material 
more  effectively. 

(5)  When  the  amount  of  lettering  is  held  to  a  minimum,  verti- 

^o  —  ro  c*>  *k  tn  o  ^ 


HARD    RUBBER             ^- 


.                 '— 

-      —  




^-  • 






_—  —  w 


)                          20                        40                        60                         80                         100                      12 



FIG.  1.     Original  chart  for  lantern  slide  (9  X  63/s  in.,  including  margins); 
exactly  1/2  actual  size. 

cal  Gothic  capitals  are  recommended  as  being  highly  legible  and 
easy  to  construct.     (See  accompanying  charts.) 

For  the  average  lecture  hall  or  auditorium,  legibility  throughout 
the  hall  is  obtained4  if  the  smallest  lettering  on  the  slide  consists  of 
capital  Gothic  letters  0.040  inch  to  0.045  inch  high,  having  a  line 
width  of  about  0.006  inch.  It  is  recommended  that  in  preparing 
charts  for  lantern  slide  use,  the  original  chart  be  made  three  tunes 
the  final  lantern  slide  size,  in  which  case  the  smallest  letters  should 
be  made  about  one-eighth  inch  high  with  a  line  width  of  about  0.017 
inch.5  (See  Figs.  1  and  2.) 



[J.  S.  M.  P.  E. 

For  charts  with  very  little  lettering  that  are  not  to  be  used  for 
publication,  a  somewhat  larger  size  of  letter  is  suggested. 

(6)  In  general,  a  satisfactory  lantern  slide  can  be  produced  by 
using  lettering  of  substantially  the  same  size  throughout.     Titles, 
if  included,  should  be  made  slightly  larger. 

(7)  All  lettering  and  numbers  on  a  slide  should  be  placed  hori- 
zontally, if  practicable.     Any  lettering  or  numbers  for  which  this  is 
not  practicable  should  face  toward  the  right-hand  side  of  the  slide. 

100  120 

FIG.  2.  Fig.  1  reduced  to  lantern  slide  size  (one-third  original  chart  dimen- 
sions). Lettering:  height  of  letters,  H-3;  width  of  line,  W-2.  Lines:  curve, 
2J/2  points;  reference  line,  ll/%  points;  grid  rulings,  */2  point. 

(8)  The  chart  should  be  precise  in  execution   so  as  to  lend  an 
impression  of  reliability. 



(9)  The  curve  is  the  most  important  element  of   a   chart  and 
should  have  the  heaviest  weight  of  line6  to  distinguish  it  sharply 
from  the  background. 

Feb.,  1933] 



(10)  Ordinarily,  not  more  than  three   curves   should  be  shown 
on  the  same  chart.     This  limitation  does  not  apply  to  curves  that 
are  similar  in  shape  and  well  separated. 

(11)  If  the  curve  represent  a  series  of  observations,    the    ob- 
served points  should  be  shown,  provided  that  by  so  doing,  additional 
essential  information  is  given  as  to  the  character  of  the  data  or  as 
to  the  reliability  of  the  curve.     Observed  points  should  preferably 
be  represented  by  circles  or  other  closed  symbols  rather  than  by 











CH                POWER    TRANSMITTED   BY   BELTING 

M                                                   DOUBLE   MACHINE-BELT 













)                                  2000                              4000                              6000                               800O 


FIG.  3.  Another  illustration  of  a  horizontal  chart.  Lettering:  title  height 
of  letters,  H-l;  width  of  line,  W-l.  Sub-title,  scale  numbers,  scale  captions: 
height  of  letters,  H-3;  width  of  line,  W-2. 

crosses.     For  such  symbols,  a  minimum  width  of  line  should  be  used. 

Grid   Rulings 

(12)  Grid  rulings  should  be  limited  in  number  to   those  neces- 
sary to  guide  the  eye  for  an  approximate  reading. 

Closely  spaced  grid  rulings  are  appropriate  for  computation  charts, 
but  not  for  charts  prepared  merely  to  show  relation. 

(13)  Grid  rulings,   including  boundaries  of   the   grid   area  but 



[J.  S.  M.  p.  E. 

excluding  reference  lines,  should  have  the  lightest  weight  of  any 
lines  on  the  chart. 

(14)     Principal  lines  of  reference,  such  as   the  zero  line,  should 
be  made  heavier  than  other  rulings  but  lighter  than  the  curves. 

Unit  of 








Number  of 

Grid  Rulings 

HORSE  HEAD      / 

0  50  tOO  ISO  200 


Grid  Rulings  Break  at 
Labels  and  Symbols 

Closed  Symbols  for 
Observed  Points 

Position  of 
Slide  Number 

(Thumb  Spot) 

FIG.  4.     Illustration  of  a  vertical  chart  (size  of  original  6  X  8l/4  in.,  including 


(15)  Grid  rulings  should  not  run  through  any  lettering  on  the 
chart  nor  through  circles  representing  observed  points. 

Scales,  Scale  Captions,  and  Designations 

(16)  Scales  and  scale  captions  should  usually  be  placed  at  the 
left  and  at  the  bottom  of  the  chart.     The  scale  caption  for  the  verti- 

Feb.,  1933  J 




Size  of  Letters 

Sample  Letters 



Approx.  Height, 







Line  Width  of  Letters 
Sample  Line 


Approx.  Width, 






See  the  Appendix  for  information  on  height  of  letters  and  width  of  lines  for 
several  commercial  lettering  templates  and  pens. 


Line  Widths 

Lines                                  Designation 



D          •         A          Q                      H  point 

148  CHARTS  FOR  LANTERN  SLIDES  [j.  s.  M.  p.  E. 

cal  scale  should  if  practicable  be  arranged  in  horizontal  lines  above 
the  upper  end  of  the  scale. 

(17)  The  horizontal  (independent  variable)  scale   values  should 
usually  progress  from  left  to  right,   and  the  vertical   (dependent 
variable)  scale  values  from  bottom  to  top. 

(18)  The  scale  caption  should  indicate  both  the  quantity  mea- 
sured and  the  unit  of  measurement. 

(19)  For  arithmetical  scales,  the  scale  figures  shown  on  the  chart 
and  the  space  between  grid  rulings  should  preferably  correspond  to 
1,  2,  or  5  units  of  measurement,  multiplied  or  divided  by  1,  10,  100,  etc. 

(20)  Scales  should  be  chosen  with  a  view  to  making  full  use  of  the 
grid  area.     When  the  zero  line  is  a  principal  standard  of  reference,  it 
should  appear  on  the  chart  if  its  presence  clarifies  the  meaning  of  the 

(21).  Curves  should  usually  be  designated  by  word-labels  placed 
horizontally  close  to  the  curves,  rather  than  by  key  letters  or  num- 
bers. When  necessary,  an  arrow  can  be  drawn  to  connect  label  and 


Note  1. — Attention  is  called  to  the  possibilities  of  using  negative  slides  and 
colors.  "Negative"  slides  (white  lines  on  black  background)  are  less  fatiguing 
to  the  audience  and  cost  less  than  "positives";  but  should  be  used  only  in  a 
thoroughly  darkened  room.  If  there  be  any  doubt  on  this  question,  it  is  safer 
to  use  "positives." 

Appropriate  use  of  color  increases  the  effectiveness  of  slides.  If  there  is  any 
likelihood  of  publishing  the  chart,  a  black  and  white  original  should  be  used 
and  the  coloring  done  by  hand  on  the  slide.  A  colored  original  satisfactory 
for  making  a  colored  slide  by  direct  color  photography  must  be  redrawn  in 
black  and  white  for  publication.  Colored  slides  cost  more  than  black  and  white 
ones  and  the  technic  is  beyond  the  scope  of  this  brochure. 

Note  2. — While  most  publications  have  their  own  standards  of  line  widths  for 
engineering  charts,  the  committee  finds  that  the  following  give  results  that  are 
representative  of  good  current  practice: 

(a)     Line  widths  on  original  chart: 

Curves — lx/2  to  2  points  (depending  on  nature  and  number  of  curves) 

Reference  Lines — 1  point. 

Grid  Rulings — Vz  point. 

(See  Tables  I  and  II  for  examples  of  line  widths  designated  by  "points.") 
(&)     Original  charts  to  be  reduced  to  one-half  original  dimensions  for  use  as 

illustrations  for  publication  (and  to  one-third  original  dimensions  for 

use  as  lantern  slides). 

Feb.,  1933]  CHARTS  FOR  LANTERN  SLIDES  149 

Note  3. — Although  slightly  more  area  is  possible  with  proportions  more  nearly 
square,  the  Committee  feels  that  those  recommended  provide  a  proper  compro- 
mise between  maximum  area,  pleasing  proportions,  opportunity  for  choice 
between  vertical  and  horizontal  presentation,  and  use  of  the  same  original  for  a 
variety  of  media. 

Note  4. — The  recommended  size  of  lettering  and  width  of  line  for  letters  are 
based  on  ophthalmological  data,  actual  tests,  and  an  investigation  of  the  condi- 
tions under  which  standard  projection  equipments  are  used. 

The  ratio  of  the  preferred  height  of  letter  on  the  screen  to  the  distance  to  the 
farthest  spectator  is  1:300 — that  is,  1-inch  letter  for  25-foot  distance,  2- inch 
letter  for  50-foot  distance,  etc.  The  recommendations  of  paragraph  5  give  this 
ratio  for  the  following  typical  conditions: 

(a)  The  lens  of  the  projection  lantern  has  a  12-inch  focal  length. 

(b)  The  farthest  spectator  is  at  the  same  distance  from  the  screen  as  the 

lantern.     (Under  average  conditions,  the.  lantern  is  rarely,  of  necessity, 
placed  closer  to  the  screen  than  the  farthest  spectator.) 

For  these  conditions,  the  width  of  image  of  a  3-inch  lantern  slide  opening  is 
equal  to  l/\  the  distance  from  screen  to  farthest  spectator.  For  the  exceptional 
case,  the  following  simple  calculation  gives  the  preferred  size  of  letter: 

(distance,  farthest  spectator  to  screen) 

Height  of  letter  on  slide,  in  inches  =  0.040  X   -  — — 

(distance,  lantern  to  screen) 

(focal  length  of  lens,  in  inches) 


The  Committee  finds  further  that  the  recommended  size  of  lettering  is  just 
legible  to  a  spectator  located  at  lantern  distance  from  the  screen,  if  a  lens  of 
18-inch  focal  length  is  used. 

The  Committee  has  assembled  data  indicating  that  slides  made  according  to 
the  recommended  practice  of  paragraph  5  are  satisfactory  in  almost  all  cases. 

Note  5. — This  is  easily  done  by  the  use  of  commercial  lettering  guides  and 
pens  provided  for  this  purpose.  The  appended  table  gives,  for  reference  pur- 
poses, the  height  of  letters  and  width  of  line  for  several  commercial  lettering 
templates  and  lettering  pens. 

Where  experienced  technic  is  available,  modification  of  these  recommendations 
as  to  style  and  size  of  lettering  may  be  found  justified. 

In  cases  where  slides  must  be  prepared  on  short  notice,  comparable  results 
may  be  obtained  by  using  pica  size  typewriter  lettering  (10  letters  to  the  inch) 
with  an  original  chart  size  of  5x/4  X  7J/2  inches,  reducing  the  chart  to  about 
40  per  cent  of  its  original  dimensions.  Although  this  gives  the  recommended 
size  of  lettering,  slides  made  in  this  way  may  be  somewhat  less  legible  than 
those  made  with  the  template  lettering  suggested,  due  in  part  to  the  lesser  black- 
ness and  sharpness  of  line  for  typewriter  lettering. 

Note  6. — The  weight  of  line  for  a  family  of  curves  may  be  made  slightly  lighter, 
and  for  a  single  curve  slightly  heavier  than  the  average  shown  in  Fig.  1  (21/2 
points).  Cf.  Figs.  2,  3,  and  4. 




Table  of  Commercial  Lettering  Templates  and  Lettering  Pens 



Wood-Regan  Instru- 
ment Co., 
New  York,  N.  Y 

Keuffel    and    Esser 
New  York,  N.  Y. 









used  with 



used  with 



used  with 



used  with 



used  with 



used  with 





No.  6 


No.  7 


No.  7 



No.  2 


No.  0 


No.  0 



"Summary  and  Report  of  Joint  Committee  on  Standards  for  Graphical  Pre- 
sentation," published  by  the  A.  S.  M.  E.  in  December,  1915.  Out  of  print. 

BRINTON,  W.  C.:  "Graphic  Methods  for  Presenting  Facts,"  Engineering 
Magazine  Company,  New  York,  N.  Y.,  1914. 

BROWN,  T.  H.:  "Laboratory  Handbook  of  Statistical  Methods,"  McGraw- 
Hill  Book  Company,  Inc.,  New  York,  1931. 

HASKELL,  A.  C.:  "How  to  Make  and  Use  Graphic  Charts,"  Codex  Book 
Company,  Norwood,  Mass.,  1919. 

KARSTEN,  K.  G.:   "Charts  and  Graphs,"  Prentice-Hall,  Inc.,  New  York,  1923. 

KiGGLEMAN,  J.  R.,  AND  FRiSBEE,  I.  N.:  "Business  Statistics,"  McGraw-Hill 
Book  Company,  Inc.,  New  York,  1.932. 

*  The  Appendix  is  added  for  information  only. 
Recommended  Practice 

It  does  not  form  part  of  the 



126  N.  Vista  St.,  Los  Angeles,  Calif. 

Kodak  Pathe  Research  Laboratory, 
30  Rue  des  Vignerons,  Vincetmes 
(Seine),  France. 
ADAIR,  S.  E.  (M) 

Jenkins    &    Adair,    3333    Belmont 

Ave.,  Chicago,  111. 

Falkenried,  16,  Berlin-Dahlem,  Ger- 
ALBIN,  F.  G.  (4) 

1030  S.  Arapahoe  St.,  Los  Angeles, 


British  International  Pictures,  Ltd., 

Elstree,  Herts,  England. 

Alexander    Film    Industries,     Inc., 

Colorado  Springs,  Colo. 

P.  O.  Box  1000,  Hollywood,  Calif. 
ANDERS,  HUGO  (-4) 

Jam  Handy   Picture  Service,   6227 

Broadway,  Chicago,  111. 
Automatic  Musical  Instrument  Co., 
1500  Union  Ave.,  S.   E.,   Grand 
Rapids,  Mich. 

26  Wedgwood  St.,  Squantum,  Mass. 

Akeley  Camera,  Inc.,  175  Varick  St., 

New  York,  N.  Y. 
ATKINSON,  S.  C.  (4) 

Regina   Photo   Supply,   Ltd.,    1924 
Rose  St.,  Regina,  Sask.,  Canada. 

BADGLEY,  F.  C.  (M) 

Canadian  Government  Motion  Pic- 
ture     Bureau,      Ottawa,      Ont., 

Shortwave  &  Television  Corp.,   70 

Brookline  Ave.,  Boston,  Mass. 

20  McEldowny  St.,  Chicago  Heights, 

BAKER,  JUDD  O.  (Af) 

RCA  Victor  Co.,  Camden,  N.  J. 
BAKER,  RAY  J.  (A) 

1911     Kalakaua     Ave.,     Honolulu, 

BAKER.  W.  R.  G.  (M) 

RCA  Victor  Co.,  Camden,  N.  J. 
BAKHSHI,  M.  N.  (A) 

P.   O.   Hill,   Bagham,   Via  Jhelum, 

Punjab,  India. 
Brooklyn  Edison  Co.,  380  Pearl  St., 

Brooklyn,  N.  Y. 
BALL,  J.  A.  (M) 

Technicolor  Motion  Picture  Corp., 
823  N.  Seward  St.,  Hollywood, 

Moving  Picture  Theater  Managers 
Institute,    315    Washington    St., 
Elmira,  N.  Y. 
BAMFORD,  WM.  B.  (4) 

614  10th  Ave.,  Belmar,  N.  J. 
BANKS,  CHAS.  (4) 

Regent    Theater,     Gisborne,     New 

BARRELL,  C.  W.  (M) 

Western  Electric  Co.,  120  W.  41st 
St.,  New  York,  N.  Y. 

*(M)  Active  Member 
(.4)  Associate  Member 




[J.  S.  M.  P.  E. 


Metropolitan  Theater,  Boston,  Mass. 

Carl  Zeiss,  Inc.,  485  Fifth  Ave.,  New 

York,  N.  Y. 
BARZEE,  G.  W.  (A) 

Caixa  Postal  494,  Sao  Paulo,  Brazil. 
Bass  Camera  Co.,  179  W.  Madison 

St.,  Chicago,  111. 
BATSEL,  MAX  C.  (M) 

RCA  Victor  Co.,  Camden,  N.  J. 

57  Shaler  Ave.,  Cliffside,  N.  J. 
BAUER,  KARL  A.  (4) 

Carl    Zeiss,    Inc.,    485    Fifth    Ave., 

New  York,  N.  Y. 

National  Theater  Supply  Co.,   500 

Pearl  St.,  Buffalo,  N.  Y. 

420  Clinton  Ave.,  Brooklyn,  N.  Y. 

Assoc.  of  Mot.  Pict.  Producers,  Inc., 
5504     Hollywood     Blvd.,     Holly- 
wood, Calif. 

RCA  Victor  Co.,  153  E.   24th   St., 

New  York,  N.  Y. 

21-24  Thirty-first  St.,  Astoria,  L.  I., 

N.  Y. 

655  E.  233rd  St.,  New  York,  N.  Y. 

112  E.  73rd  Street,  New  York,  N.  Y. 

1  Rue  du  Chemin  de  Fer,  a  Croissy, 


79  Blvd.  Haussmann,  Paris,  France. 

Compagnie  Radio  Cinema,  79  Blvd. 
Haussmann,  Paris,  VIII,  France. 

Kiddle,  Margeson,  &  Hornidge,  511 
Fifth    Ave.,    New    York,    N.    Y. 


Bell    Telephone    Laboratories,    463 

West  St..  New  York,  N.  Y. 
BIELICKE,  WM.  F.  (M) 

Astro-Gesellschaft  m.  b.  h.,  Lahnstr., 

30,  Berlin-Neukolln,  Germany. 

820  N.   Martel  Ave.,   Los  Angeles, 


Eastman  Kodak  Co.,  343  State  St., 

Rochester,    N.    Y. 
BLAKE,  E.  E.  (A) 

Kodak,  Ltd.,  63  Kingsway,  London, 

W.  C.  2,  England. 
BLANEY,  J.  M.  (M) 

51  Sterling  Place,  Amityville,  L.  I., 

N.  Y. 

1403  N.  Orange  Grove,  Hollywood, 

BLIVEN,  J.  E.  (M) 

Box  91,  New  London,  Conn. 

Prinzregentenstr.,     93,     Berlin-Wil- 

mersdorf,  Germany. 

Agfa  Ansco  Corp.,  Camera  Works, 

Johnson  City,  N.    Y. 
BOYLEN,  JOHN  C.  (-4) 

Ontario  Govt.  M.  P.  Bureau,  Parlia- 
ment    Bldgs.,      Toronto,      Ont., 
BRADFORD,    ARTHUR    J.    (4) 

Jam   Handy   Picture   Service,   2900 
E.    Grand   Blvd.,    Detroit,   Mich. 
BRADSHAW,  A.  E.  (4) 

1301  Sixth  Ave.,  Tacoma,  Wash. 

Fox  Hearst  Corp.,  460  W.  54th  St., 

New  York,  N.  Y. 

320  E.  176th  St.,  New  York,  N.  Y. 

Mechanische.  Optische  Werkstatten, 
G.  m.  b.  h.,  Potsdamerstr.,  38, 
Berlin,  W.  35,  Germany. 

Feb.,  1933] 



BREWSTER,  P.  D.  (M) 

Brewster  Color  Film  Corp.,  58  First 

St.,  Newark,  N.  J. 

1041   N.    Formosa   St.,   Hollywood, 

BROCK,  GUSTAV  F.  O.  (A) 

528  Riverside  Dr.,  New  York,  N.  Y. 

22  Ormond  Ave.,  Oaklyn,  N.  J. 

704  S.  Spring  St.,  Los  Angeles,  Calif. 
BUCKLES,  J.  O.  (A) 

1609  W.  40th  St.,  Oklahoma  City, 


Carrier  Engineering  Corp.,  Chrysler 
Building,  New  York,  N.  Y. 

BURCHETT,    C.    W.    04) 

Theater  Lighting  &  Equipment  Co., 
255  Golden  Gate  Ave.,  San  Fran- 
cisco, Calif. 
BUREL,  L.  H.  (A) 

5  Rue  Leon  Coquiet,  Paris,  XVII, 


Camera    Dept.,    Paramount    Publix 
Corp.,  5451  Marathon  St.,  Holly- 
wood, Calif. 

RCA  Radiotron  Co.,  415  S.  5th  St., 

Harrison,  N.  J. 

70  Rue  Lauriston,  Paris,  France. 
BURNETT,  J.  C.  (M} 

Burnett-Timken    Research    Labora- 
tory, Alpine,  N.  J. 
BURNS,  ROBERT  P.  (^4) 

3034    Leland    Ave.,     Chicago,    111. 
BURNS,  S.  R.  (M) 

International    Projector    Corp.,    90 

Gold  St.,  New  York,  N.  Y. 

1306  S.  Michigan  Ave.,  Chicago,  111. 
BUSCH,  LEO  N.  (A) 

Kodak     A.-G.,     Friedrichshagener- 
str.,  9,  Berlin-Copenick,  Germany. 

Agfa    Ansco     Corp.,     Binghamton, 

N.  Y. 

1030    W.    49th    St.,    Los   Angeles, 


General  Electric  Vapor  Lamp  Co., 
Hoboken,  N.  J. 


Pathescope,  Ltd.,  5  Lisle  St.,  Leices- 
ter Sq.,  London,  W.  C.  2,  England. 
CAHILL,  FRANK  E.,  JR.  (M] 

Warner   Bros.    Theaters,    Inc.,    321 

W.  44th  St.,  New  York,  N.  Y. 

Cameron    Publishing    Co.,    Wood- 

mont,  Conn. 
CANADY,  DON  R.  (If) 

19570  S.  Sagamore  Rd.,  Cleveland, 

CANTRELL,  W.  A.  (4) 

503  East  Prescot  Road,  Knotty  Ash, 

Liverpool,  England. 
Research  Laboratories,  Eastman  Ko- 
dak Co.,  Rochester,  N.  Y. 
J.  L.  Carlton  Labs.,  Inc.,  90-25  Co- 
rona Ave.,  Elmhurst,  L.  I.,  N.  Y. 
CARPENTER,  A.  W.  (A) 

United  Research  Co.,  41-40  Harold 
Ave.,   Long  Island   City,   N.   Y. 

Escar  Motion  Picture  Service,  Inc., 
10008  Carnegie  Ave.,  Cleveland, 

CARSON,  W.  H.  (M) 
Agfa    Ansco     Corp.,     Binghamton, 

N.  Y. 

1254  E.  31st  St.,  Brooklyn,  N.  Y. 
CASS,  JOHN  L.  (M) 

RCA  Victor  Co.,  Camden,  N.  J. 
CECCARINI,  O.  O.  (M) 

Metro-Goldwyn-Mayer  Studios,  Cul- 
ver City,  Calif. 



[J.  S.  M.  P.  E. 


Eastman    Kodak    Co.,    6706    Santa 
Monica  Blvd.,  Hollywood,  Calif. 
.     Old  Short  Hills  Road,  Short  Hills,  NJ. 

Glendale,  Calif. 
CHARNEY,  FELIX  A.  (^4) 
8827     Woodhaven     Blvd.,     Wood- 
haven,  L.  I.,  N.  Y. 

22  Rue    de    Civry,     Paris,     XVI, 

J.  Frank  Brockliss,  Ltd.,  58  Great 

Marlborough  St.,  London,  W.  1, 


23  Rue  Preschez,  St.  Cloud,  France. 
CIFRE,  J.  S.  (M) 

National  Theater  Supply  Co.,  211 
Columbus    Ave.,    Boston,    Mass. 

1147  Hartzell  St.,  Pacific  Palisades, 


2327     Glendon     Ave.,     West     Los 

Angeles,  Calif. 
CLARK,  REX  S.  (M) 

Clark  Cine  Service,  203  Professional 

Bldg.,  Detroit,  Mich. 
Research     Laboratories,      Eastman 

Kodak  Co.,  Rochester,  N.  Y. 

94-30   46th   Ave.,  Elmhurst,  L.  I., 

N.  Y. 
CLAYTON,  ROY  S.   (4) 

Metropolitan  Sound  Studio,  Holly- 
wood, Calif. 

Columbia  Broadcasting  System,  485 
Madison  Ave.,  New  York,  N.  Y. 

Atlantic     Gelatin     Co.,     Hill     St., 

Woburn,  Mass. 

Rabun    Theater,    Clayton,    Ga. 


Pathescope  Co.  of  America,  Inc.,  33 
W.  42nd  St.,  New  York,  N.  Y. 


Blue  Seal  Sound  Devices,  Inc.,  130 

W.  46th  St.,  New  York,  N.  Y. 
COOK,  ALAN  A.  (A) 
Bausch  &  Lomb   Optical   Co.,   635 

St.  Paul  St.,  Rochester,  N.  Y. 
COOK,  OTTO  W.  (M) 

Eastman    Kodak    Co.,    343    State 

Street,  Rochester,  N.  Y. 

Kodascope   Libraries,   33   W.   42nd 

St.,  New  York,  N.  Y. 
COOLEY,  W.  D.  (A) 

RCA  Victor  Co.  of  China,  Shanghai, 


1819    G   St.,    N.   W.,   Washington, 

D.  C. 

COUR,  EUGENE  J.  (If) 
Pathe  News,  1023  S.  Wabash  Ave., 

Chicago,  111. 
COURCIER,  J.  L.  (A) 

J.   E.   Brulatour,   Inc.,   6700  Santa 
Monica  Blvd.,  Hollywood,   Calif. 

Academy  of  Motion  Picture  Arts  & 
Sciences,  7046  Hollywood  Blvd., 
Hollywood,  Calif. 

311  Alexander  St.,  Rochester,  N.  Y. 

877  Sterling  Place,  Brooklyn,  N.  Y. 
COZZENS,  Louis  S.  (M} 

Du   Pont  Film   Mfg.    Co.,    Parlin, 

N.  J. 

Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 

Research  Laboratories,  Eastman  Ko- 
dak Co.,  Rochester,  N.  Y. 

Shirley  Court,  Stonehurst,  Pa. 

Feb.,  1933] 



CRENNAN,  OLLIE  V.  (^4) 
200  Eastchester  Road,  New  Rochelle, 

N.  Y. 

Cinecolor  Inc.,   201   N.    Occidental 

Blvd.,  Hollywood,  Calif. 

5923    Beach  Drive,  Seattle,  Wash. 

131  Gladstone  Ave.,  Windsor,  Ont., 


12  Maiden  Lane,  New  York,  N.  Y. 
Agfa  Raw  Film  Corp.,  1328  Broad- 
way, New  York,  N.  Y. 

RCA  Victor  Co.,  Camden,  N.  J. 
Box  1614,  Station  A,  Chattanooga, 


Eastman    Kodak    Co.,    343    State 
Street,  Rochester,  N.  Y. 

Material    Cinematographique,    111, 
113    Rue     St.  Maur,   Paris,  XI, 

DANA,  ALAN  S.  (A) 
Kerite  Insulated  Wire  &  Cable  Co., 

Seymour,  Conn. 

21  Nadeshjeanskaya,  Apt.  20,  Lenin- 
grad, U.  S.  S.  R. 
D'ARCY,  E.  W.  U) 
Spoor-Ahbe    Studios,    1245    Argyle 

St.,  Chicago,  111. 
DASH,  C.  C.  (Jlf) 

Hertner  Electric   Co.,    12690   Elm- 
wood  Ave.,  Cleveland,  Ohio. 

153  Westervelt  Ave.,  Tenafly,  N.  J. 
Roy    Davidge    Film    Laboratories, 
6701  Santa  Monica  Blvd.,  Holly- 
wood, Calif. 

DAVIDSON,  L.  E.  (.4) 

775  Main  St.,  Buffalo,  N.  Y. 

Material    Cinematographique,    111, 
113  Rue  St.  Maur,  Paris,  France. 
Villa  Medioevale  Torlonia,  via  Laz- 

zaro  Spallanzani,  Rome,  Italy. 

6    bis,    Rue    Laure    Fiot,    Asni&res 

(Seine),  France. 
8190  Hollywood  Blvd.,  Hollywood, 


De   Frenes   Co.,   60  N.   State  St., 

Wilkes-Barre,  Pa. 

101   Liberty  Ave.,  Mineola,  L.  I., 

N.  Y. 

Kodak    Japan,    Ltd.,    3-Nishiroku- 

chome,  Ginza,  Tokyo,  Japan. 
DE  Moos,  CHARLES  (A) 

Du  Pont  Film  Mfg.  Co.,  Parlin,  N.  J. 
Burton  Holmes  Lectures,  Inc.,  7510 

N.  Ashland  Ave.,  Chicago,  111. 
DEPUE,  O.  B.  (M} 

7512  N.  Ashland  Ave.,  Chicago,  111. 

Gevaert  Co.  of  America,  Inc.,  423 
W.   55th  St.,  New  York,  N.  Y. 

Surya  Film  Co.,  5  Cunningham  Rd., 
Bangalore    City,    Mysore    State, 

Film6fono,  S.  A.,  4  Plaza  del  Callao, 

Madrid,  Spain. 
DEVRY,  H.  A.  (M) 

1111  Center  St.,  Chicago,  111. 
DsWiTT,  H.  N.  (A) 

36  Toronto  St.,  Toronto,  Ont.,  Can. 

Motion  Picture  Prod.  &  Dist.  of 
America,  Inc.,  28  W.  44th  St.,  New 
York,  N.  Y. 



[J.  S.  M.  p.  E. 

DlDIEE,  L.  J.  J.    (4) 

Societe  Kodak-Pathe,  39  Ave.  Mon- 
taigne, Paris,  France. 
DIETERICH,  L.  M.  (M) 
2026  Holly  Hill  Terrace,  Hollywood, 


494  Dwas  Line  Road,  Clifton,  N.  J. 
DODDRELL,  E.  T.  JR.  04) 

151  Wainui  Road,  Kaiti,  Gisborne, 

New  Zealand. 

Metro  -  Goldwyn  -  Mayer  Studios, 

Culver  City,  Calif. 
DONER,  FRANK  M.  (^4) 

Station  B,  P.  O.  Box  6,  Toledo,  Ohio. 

Menlo  Park,  Calif. 
DOWNES,  A.  C.  (M) 

National    Carbon    Co.,    Box    400, 

Cleveland,  Ohio. 

RKO  Studios,  Inc.,  780  Gower  St., 

Hollywood,  Calif. 
Bell  &  Howell  Co.,  716  No.  La  Brea 

Ave.,  Hollywood,   Calif. 

Fairmont  Theater,  Fairmont,  W.  Va. 

Patent    Research,    Inc.,    521    Fifth 

Ave.,  New  York,  N.  Y. 

Dunning   Process   Co.,   932   N.    La 

Brea  Ave.,    Hollywood,    Calif. 

Dunning   Process   Co.,    932   N.    La 

Brea  Ave.,  Hollywood,  Calif. 

Thos.  A.  Edison,  Inc.,  West  Orange, 

DURHOLZ,  OTTO  B.  (^4) 

21  Martin  St.,  Paterson,  N.  J. 

RCA  Victor  Co.,  Camden,  N.  J. 

DWYER,  RAYMOND  J.  (^4) 

Eastman  Kodak  Co.,  343  State  St., 

Rochester,  N.  Y. 
Dyke  Cinema  Products  Co.,  133-12 
228th  St.,  Laurelton,  L.  L,  N.  Y. 


Agfa     Ansco     Corp.,     Binghamton, 

N.  Y. 

Thos.  A.  Edison,  Inc.,  West  Orange, 

EDOUART,  A.  F.  (A) 

Paramount  Publix  Corp.,  5451  Mara- 
thon St.,   Hollywood,   Calif. 

49  Trafalgar  Square,  Lynbrook,  L.  I., 

N.  Y. 

58  Blvd.  National,  Vincennes,  Seine, 


2240  Ogden  Ave.,   Chicago,  111. 

10   Westbury   Ave.,    Staten    Island, 

N.  Y. 
ELWELL,  CYRIL  F.  (.4) 

197  Queens  Gate,  London,  S.  W.  7, 


907  W.  Hamilton  St.,  Flint,  Mich. 
ENGL,  JOSEF  B.  (M) 

Bismarckstr.,  97,  Berlin- Charlotten- 

burg,  Germany. 

Wilcza  str.  29a/12,  Warsaw,  Poland. 
Warner  Bros.    Pictures,   Inc.,    1277 

E.  14th  St.,  Brooklyn,  N.  Y. 

De    Luxe    Laboratories,    Inc.,    441 

W.  55th  St.,  New  York,  N.  Y. 

Division  of  Motion  Pictures,  U.  S. 
Dept.  of  Agriculture,  Washington, 
D.  C. 

Feb.,  1933] 




Archibald    Nettlefold    Productions, 
The   Studios,  Hurst  Grove,  Wal- 
ton-on-Thames,  England. 

Kodak,  S.  P.  z.  o.  o.,  5  Place  Na- 
poleon, Warsaw,  Poland. 
FARNHAM,  R.  E.  CM) 

Engr.   Dept.,  General  Electric  Co. 

Nela  Park,   Cleveland,  Ohio. 

United  Research  Corp.,  321  W.  44th 

St.,  New  York,  N.  Y. 

117  W.  45th  St.,  New  York,  N.  Y. 
FAYE,  JAMES  J.  (A) 

Racquet  and  Tennis  Club,  370  Park 

Ave.,  New  York,  N.  Y. 

2010  Sixth  Ave.,  Los  Angeles,  Calif. 

Chicago  Film  Lab.,  Inc.,  1322  Bel- 
mont  Ave.,  Chicago,  111. 

FINN,  JAMES  J.  (A} 

1  W.  47th  St.,  New  York,  N.  Y. 
Kodak,    Ltd.,    Wealdstone,  Middle- 
sex, England. 

Electrical  Research  Products,   Inc., 
250  W.  57th  St.,  New  York,  N.  Y. 

Fleischer  Studios,  Inc.,  1600  Broad- 
way, New  York,  N.  Y. 
FLINT,  ASHER  (.4) 

8  Jochum  Ave.,  Larchmont,  N.  Y. 
FLORY,  Louis  P.  04) 

Boyce-Thompson  Institute,  1086  N. 

Broadway,  Yonkers,  N.  Y. 

Celluloid  Co.,  290  Ferry  St.,  Newark, 

N.  J. 
FOOTE,  PAUL  C.  (A) 

Bell  &  Howell  Co.,  4045  N.  Rockwell 
St.,  Chicago,  111. 


Afritone  Productions,  Ltd.,  Braeside, 
Herschel  Walk,  Wynberg,  C.  P., 
South  Africa. 
FORD,  BERT.  (A) 

3    Belmont    House,    Candover    St., 

London,  W.  1,  England. 

Kinatome  Patents  Corp.,  4  Wilsey 

Sq.,  Ridgewood,  N.  J. 

The    Turning,    Kinsbourne    Green, 

Harpenden,  Herts,  England. 

RCA  Victor  Co.,  Camden,  N.  J. 
FRANK,  KARL  G.  (M) 

75  West  St.,  New  York,  N.  Y. 

RKO  Pictures,  Inc.,  1560  Broadway, 

New  York,  N.  Y. 

United   Film    Industries,    Inc.,    420 

Madison  Ave.,  New  York,  N.  Y. 

Electrical  Research  Products,   Inc., 
7046  Hollywood  Blvd.,   Los  An- 
geles, Calif. 

De  Luxe  Laboratories,  Inc.,  441  W. 

55th  St.,  New  York,  N.  Y. 

3093  Lake  Hollywood  Drive,  Holly- 
wood, Calif. 

Eastman    Kodak    Co.,    343    State 
Street,  Rochester,  N.  Y. 

GAGE,  HENRY  P.   (M) 

Corning     Glass     Works,      Corning, 

N.  Y. 
GAGE,  OTIS  A.  (A) 

Corning     Glass     Works,      Corning, 

N.  Y. 

c/o  Wasserman,  2823  Hubbard  St., 
Brooklyn,  N.  Y. 



[J.  S.  M.  p.  E. 

GARLING,  W.  F.  (M) 

RCA  Photophone,  Inc.,  Film  House, 

Wardour  St.,  London,  England. 
GEIB,  E.  R.  (M) 

National    Carbon    Co.,    Box    400, 

Cleveland,  Ohio. 
GELMAN,  J.  N.  (M) 

3439  Jays  St.,  Cincinnati,  Ohio. 

1    Trevanion   Rd.,    West   Kensing- 
ton,   London,    W.    14,    England. 
J.  E.  Brulatour,  Inc.,  154  Crescent 

St.,  Long  Island  City,  N.  Y. 
46  Jayson  Ave.,  Great  Neck,  L.  I., 

N.  Y. 
GEYER,  KARL  (-4) 

Geyer-Werke,  A.-G.,  Harzerstr.  39/- 

42,  Berlin,  S.  O.  36,  Germany. 
Treptower  Park,  59,  Berlin,  S.  O. 

36,  Germany. 
J.   E.  Brulatour,  Inc.,  6700  Santa 
Monica  Blvd.,  Hollywood,  Calif. 
J.  L.  Nerlien,  Ltd.,  Nedre  Slottsgate- 

13,  Oslo,  Norway. 
GILMOUR,  JOHN  G.  T.  (A) 
Visual  Instruction  Section,  General 
Electric  Co.,  Schenectady,  N.  Y. 
Warner  Brothers  Theatres,   932  F 

St.,  N.  W.,  Washington,  D.  C. 
GLAUBER,  S.  (-4) 

2062  E.  37th  St.,  Brooklyn,  N.  Y. 

14    N.    Hancock    St.,    Lexington, 


1560  Ansel  Rd.,  Cleveland,  Ohio. 

Craft  Film  Labs.,  Inc.,  136-23  34th 

Ave.,  Flushing,  L.  L,  N.  Y. 
Abbey  House,  Westminster,  London, 
S.  W.  1,  England. 

GLUNT,  OMER  M.  (M) 

Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 
GOLDBERG,  Jos.  H.  (M} 

Publix  Theaters  Corp.,  Paramount 

Bldg.,  New  York,  N.  Y. 

Motion  Picture  Division,  U.  S.  Dept. 
of  Commerce,  Washington,  D.  C. 

Radio  Corporation  of  America,  570 
Lexington  Ave.,  New  York,  N.  Y. 
GOUDY,  CARL  F.  (A) 
32-15  N.  17th  St.,  Flushing,  L.  I.. 


30  Jefferson  St.,  Wellsville,  N.  Y. 

Engr.  Dept.  Camera  Works,  East- 
man Kodak  Co.,  Rochester, 
N.  Y. 

2722  Harriet  Ave.  S.,  Minneapolis, 


4531  S.   169th  St.,  Flushing,  L.  L, 

N.  Y. 
GREGORY,  CARL  Louis  (M) 

76  Echo  Ave.,  New  Rochelle,  N.  Y. 
International    Projector    Corp.,    90 

Gold  St.,  New  York,  N.  Y. 

6417  W.  6th  St.,  Los  Angeles,  Calif. 

Western   Electric   Co.,    Old   Colony 
House,    South    King    St.,    Man- 
chester, England. 

Paramount  Publix  Corp.,  5451  Mara- 
thon St.,  Hollywood,  Calif. 
Radio  Corporation  of  America,  570 
Lexington  Ave.,  New  York,  N.  Y. 

6   Sibley   Place,   Rochester,    N.   Y. 

Feb.,  1933] 




Standard    Pictures,    Ltd.,    Egerton 

Road,    Delhi,    India. 

Bijou    Theater,    Bangor,    Maine. 


9  Argyle  Road,  Brooklyn,  N.  Y. 

National  Theater  Supply  Co.,  308 

N.   Gay  St.,  Baltimore,  Md. 
HALBERTSMA,  N.  A.  04) 

Philips'  Glow  Lamps  Works,  Ltd., 

Eindhoven,  Holland. 

1600  W.  66th  St.,  Los  Angeles,  Calif. 

1835  N.  Garfield  PL,  Apt.  A.,  Holly- 
wood, Calif. 

302    N.    Oakhurst    Drive,    Beverly 

Hills,  Calif. 

2825  Linden  Ave.,  Knoxville,  Tenn. 

307  W.  107th  St.,  New  York,  N.  Y. 
HARDY,  A.  C.  (M) 

Mass.  Institute  of  Technology,  Cam- 
bridge, Mass. 

Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 
HARLOW,  JOHN  B.  04) 

Electrical  Research  Products,   Inc., 
250  W.  57th  St.,  New  York,  N.  Y. 

647  Cragmont  Ave.,  Berkeley,  Calif. 
Debrie  Etablissemente,  23  Mortimer 

St.,  London,  W.  1,  England. 
HAYDEN,  A.  C.  (M) 

A.  C.  Hayden  Co.,  Box  496,  Brock- 
ton, Mass. 

P.  O.  Box  69,  Brockton,  Mass. 

11  George  St.,  Brooklyn,  N.  Y. 

HENNESSY,    WM.    W.    (4) 
564    S.    Goodman    St.,    Rochester, 

N.  Y. 

1747   N.    Mayfield   Ave.,    Chicago, 


Pathe  News,  Inc.,  35  West  45th  St., 

New  York,  N.  Y. 
Research  Laboratories,  Eastman  Ko- 
dak Co.,  Rochester,  N.  Y. 

Eftee  Films,  His  Majesty's  Theater, 

Melbourne,  Victoria,  Australia. 

69  Gouett  St.,  Randwick,  Sydney, 


Mefropolitan  Motion  Picture  Corp., 
1745  E.  Grand  Blvd.,  Detroit, 

5319     Santa    Monica    Blvd.,     Los 

Angeles,  Calif. 
HOFFMAN,  Louis  B.  (M) 

Stuyvesant  Woods,  Rye,  N.  Y. 
HOGE,  JOSEPH  F.  D.  (M) 

Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 

894  Beck  St.,  New  York,  N.  Y. 

57  N.  22nd  St.,  East  Orange,  N.  J. 
HOLSLAG,  R.  C.  04) 

Amateur   Cinema  League,    105  W. 

40th  St.,  New  York,  N.  Y. 

29-41  167th  St.,  Flushing,  L.  L,  N.  Y. 


72  Rue  Vaneau,  Paris,  France. 

Kiddle,  Margeson  &  Hornidge,  511 
Fifth   Ave.,    New   York,    N.    Y. 
Warner  Bros.  Pictures,  Inc.,  321  W. 
44th  St.,  New  York,  N.  Y. 



[J.  S.  M.  P.  E. 

HORSTMAN,  CHAS.  F.  (^4) 
Radio-Keith-Orpheum    Corp.,    1560 

Broadway,  New  York,  N.  Y. 

General   Radio    Co.,    30   State   St., 

Cambridge,  Mass. 

Societe  de  Material  Acoustique,    1 

Blvd.  Haussman,  Paris,  France. 
HOWELL,  A.  S.  (M) 

Bell  &  Howell  Co.,  4045  N.  Rock- 
well St.,  Chicago,  111. 

Akeley  Camera,  Inc.,  175  Varick  St., 
New  York,  N.  Y. 


Consolidated   Film  Industries,  Inc., 
1776  Broadway, New  York,  N.  Y. 
HUBBARD,  WM.  C.  (M) 

111    W.    5th   St.,    Plainfield/N.    J. 

Ilford,  Ltd.,  Selo  Works,  Brentwood, 

Essex,  England. 
HULAN,  ARL  G  .  (M) 

100    N.    Goodman    Ave.,    Kerens, 


Adcraft  Film  Service,   1312  Oswego 

St.,  Utica,  N.  Y. 
Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 

Eastman    Kodak    Co.,    6706    Santa 
Monica  Blvd.,  Hollywood,   Calif. 

Eastman  Kodak  Co.,  350  Madison 
Ave.,  New  York,  N.  Y. 


1835V2  Grace  St.,  Los  Angeles,  Calif. 

400  E.  58th  St.,  New  York,  N.  Y. 
IVER,  ROBERT  W.  (4) 

Shea-Publix  Theater,  Bradford,  Pa. 
IVES,  F.  E.  (Honorary) 

1753  N.  15th  St.,  Philadelphia,  Pa. 


Pathescope    Co.    of   America,    Inc., 
33  W.  42nd  St.,  New  York,  N.  Y. 


The    Optical    Institute,    Birjevaya 
Linia  12,  Leningrad,  U.  S.  S.  R. 
JAMES,  F.  E.   (M) 

General  Electric  Co.,  5201  Santa  Fe 

Ave.,  Los  Angeles,  Calif. 

2212  Line  Oak  St.,  Dallas,  Texas. 

Metropolitan   Motion   Picture    Co., 
1745    E.    Grand    Blvd.,    Detroit, 
JAY,  RONALD  L.  (4) 

Jay's  Screen  Service,   23  Nithsdale 

Rd.,  Glasgow,  S.  1,  Scotland. 

9  Giles  St.,  Toorak,  Adelaide,  South 

JENKINS,   C.   FRANCIS   (Honorary) 

5502   16th   St.,   Washington,    D.  C. 

Jenkins  &  Adair,  Inc.,  3333  Belmont 

Ave.,  Chicago,  111. 

12a,  Putney  Hill,  London,  S.  W.  15, 


Zeiss-Ikon  A.-G.,  Schandauerstr.,  76, 

Dresden  a  21,  Germany. 

National  Bank  Bldg.,  Johannesburg, 

South  Africa. 
JONES,  JOHN  G.  (M) 

Eastman  Kodak  Co.,  Kodak  Park, 

Rochester,  N.  Y. 
JONES,  JOHN  M.,  JR.  (A) 

629  Tremont  Ave.,  Charlotte,  N.  C. 
JONES,  L.  A.  (M) 

Research  Laboratories,  Eastman  Ko- 
dak Co.,  Rochester,  N.  Y. 
JOY,  JOHN  M.  (M) 

12  Fairview  Ave.,  Yonkers,   N.  Y. 

Feb.,  1933] 




Technicolor  Motion  Picture  Corp., 
823  N.  Seward  St.,  Hollywood,  Cal. 
Motion  Picture  Service,  U.  S.  Army, 
Quarry    Heights,    Panama    Canal 

P.  O.  Box  929,  Harrisburg,  Pa. 
Western   Electric   Co.,   Ltd.,    Coles 
Green  Road,   London,   N.  W.  2, 
KELLEY,  WM.  V.  D.  (M) 

2228  Holly  Drive,  Hollywood,  Calif. 

RCA  Victor  Co.,  Camden,  N.  J. 

1312  Hudson  Rd.,  West  Englewood, 


A.    Kershaw  &  Son,   200  Harehills 

Lane,  Leeds,  England. 
KEUFFEL,  CARL  W.  (4) 

Keuffel  &  Esser  Co.,  3rd  &  Adams 
Sts.,  Hoboken,  N.  J. 

KlENNINGER,    JOHN    F.    (A) 

Technicolor  Motion  Picture  Corp., 
1016  N.  Cole  Ave.,  Hollywood, 


National   Screen   Service,    Ltd.,    25 
Denmark  St.,  London,  W.  C.  2, 

36  Crestwood  Ave.,  Buffalo,  N.  Y. 

Society  for  Visual   Education,   327 

LaSalle  St.,  Chicago,  111. 

RCA  Victor  Co.,  Hollywood,  Calif. 
KNOX,  HARRY  G.  (M} 

Electrical  Research  Products,   Inc., 
250    W.    57th    St.,    New  York, 

16  Rue  de  Chateaudun,  Asnieres 
(Seine),  France. 


Magnavox  Co.,  Ltd.,  Fort  Wayne, 

Indiana.  » 


Friedrichstr.,  46,  Berlin,  S.  W.  68, 

KROESEN,  J.  C.  (M} 

406  Belleville  Ave.,  Belleville,  N.  J. 
KRUGERS,  GEO.  E.  A.  (M} 

Krugers     Film     Corp.,     Bandoeng, 

Java,  D.  E.  I. 
KUHN,  JOHN  J.  (M} 

Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 

5412  Virginia  Ave.,  Hollywood,  Calif. 
KUNZMANN,  W.  C.  (M} 

National    Carbon    Co.,    P.    O.    Box 
400,  Cleveland,  Ohio. 

KURLANDER,   J.    H.    (M) 

Westinghouse  Lamp  Co.,  Bloomfield, 

LA  CHAPELLE,  Louis  (^4) 

Consolidated  Amusement  Co.,  P.  O. 

Box  2425,  Honolulu,  Hawaii. 
LAIR,  C.  (M) 

Kodak-Pathe,  30  Rue  des  Vignerons, 

Vincennes  (Seine),  France. 
LAMB,  ELGIE  E.  (M) 

Bell  &  Howell  Co.,  Ltd.,  320  Regent 

St.,  London,  W.  1,  England. 

Metro  -  Goldwyn  -  Mayer  Studios, 

Culver  City,  Calif. 

3832V2    Westwood    Blvd.,     Culver 

City,  Calif. 
Audio-Cinema,   Inc.,  2826   Decatur 

Ave.,  New  York,  N.  Y. 

12505  Edgewater  Drive,  Lakewood, 


RCA  Victor  Co.,  Camden,  N.  J. 



[J.  S.  M.  P.  E. 


Paramount      Publix     Corp.,      1501 

Broadway,  New  York,  N.  Y. 

6157  N.  Artesian  Ave.,  Chicago,  111. 

Paramount     Publix      Corp.,      1501 

Broadway,  New  York,  N.  Y. 
LAUSTE,  E.  A.  (Honorary) 

12  Howard  St.,  Bloomfield,  N.  J. 

Lawley    Apparatus    Co.,    Ltd.,    26 
Church    St.,    Charing    X    Road, 
London,  W.  1,  England. 
LEA,  WM.  DE  LANE  (A) 
283  Promenade  des  Anglais,   Nice, 

Alpes  Maritimes,  France. 

Royal  Zenith  Sound  Projectors,  Inc., 
33  W.  60th  St.,  New  York,  N.  Y. 
LEISHMAN,  E.  D.  (.4) 

Universal  Film  Exchanges,  Inc.,  730 

Fifth  Ave.,  New  York,  N.  Y. 

Fox  Films,  Inc.,  1401  Northwestern 

Ave.,  Los  Angeles,  Calif. 
LEVENTHAL,  J.  F.  (M) 

175  Varick  St.,  New  York,  N.  Y. 

6019  Eileen  St.,  Los  Angeles,  Calif. 
LICHTE,  H.  (M) 

Boraweg   3,    Berlin-Lankwitz,    Ger- 

S.  Guiterman  &  Co.,  Ltd.,  36  Alder- 
manbury,  London,  E.  C.  2,  Eng- 
LINS,  PERCY  A.  (A) 

Herbert  &  Huesgen  Co.,  18  E.  42nd 

St.,  New  York,  N.  Y. 

The  Replitura  Corp.,  Melrose  Ave., 

Stamford,  Conn. 
LITTLE,  W.  F.  (M) 

Electrical  Testing  Lab.,  80th  St.  & 
East  End  Ave.,  New  York, 
N.  Y. 


135  William  St.,  New  York,  N.  Y. 

14  Caryl  Ave.,  Yonkers,  N.  Y. 
LUCAS,  GEORGE  S.  C.  (A) 

British  -  Thomson  -  Houston  Co., 

Ltd.,  Rugby,  England. 

Mehta-Luhar  Productions,  167  Main 
Road,  Dadar,  Bombay,  14,  India. 

Kenton  House,  Upper  Shirley  Rd., 

Croydon,  Surrey,  England. 

6145  Glenwood  Ave.,  Chicago,  111. 
LUMIERE,  Louis  (Honorary) 

156  Blvd.  Bineau  a  Neuilly,  Paris, 

LUMMERZHEIM,     HERMANN    J.     (.4) 

I.  G.  Farbenindustrie  Aktiengesell- 
schaft,  Berlin,  S.  O.  36,  Germany. 

4404  Sixth  Ave.,  Brooklyn,  N.  Y. 

MAAS,  ARTHUR  R.  (^4) 

A.  R.  Maas  Chemical  Co.,  308  E. 

Eighth  St.,  Los  Angeles,  Calif. 
3056  7th  St.,  Jackson  Heights,  L.  I., 

N.  Y. 

Electrical  Research  Products,  Inc., 
7046      Hollywood      Blvd.,      Los 
Angeles,   Calif. 
MACKLER,  A.  I.  (M) 

Film   Renovating   Co.   of   America, 
Inc.,  630  Ninth  Ave.,  New  York, 
N.  Y. 
MACLEOD,  J.  S.  (M) 

Metro  -  Goldwyn  -  Mayer  Pictures, 
1540  Broadway,  New  York,  N.  Y. 

Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 
MAIRE,  HENRY  J.   (A) 

5640  Kingsessing  Ave.,  Philadelphia, 

Feb.,  1933] 




Malkames  Educational  Film  Co.,  705 
W.  Diamond  Ave.,  Hazleton,  Pa. 

91  Prospect  St.,  East  Orange,  N.  J. 
MANHEIMER,  J.  R.  (M) 

E.    J.    Electrical    Installation    Co., 
227  E.  45th  St.,  New  York,  N.  Y. 

1923  81st  St.,  Brooklyn,  N.  Y. 

168  Rue  de  Belleville,   Paris,  XX, 


Pathe  Cinema,  8  Rue  Leconte  de 

Lisle,  Paris,  France. 
Technical  Division,  Hercules  Pow- 
der Co.,  Wilmington,  Del. 

Eclair  Tirage,  34  a  42  Av.  d'Enghein, 

Epinay  sur  Seine,  France. 

327  23rd  St.,  Miami  Beach,  Fla. 
Research  Laboratories,  Eastman  Ko- 
dak Co.,  Rochester,  N.  Y. 
MAY,  R.  P.  (4) 

Haddonfield  Manor  Apts.,  Haddon- 

field,  N.  J. 
MCAULEY,  J.  E.  (M) 

McAuley  Mfg.  Co.  552  W.  Adams 

St.,  Chicago,  111. 
Western  Electric  Co.  (N.  Z.),  Ltd., 
Box  605,   G.   P.   O.,  Wellington, 
New  Zealand. 
Westinghouse    Elec.    &    Mfg.    Co., 
150  Broadway,  New  York,  N.  Y. 

916  St.  James  St.,  Pittsburgh,  Pa. 

McCROSKEY,   H.    E.    (4) 

2203    Broadview    Terrace,    Holly- 
wood, Calif. 

McCULLOUGH,  R.  H.    (M} 

8408  Blackburn  Ave.,  Los  Angeles, 

Agfa,  Ltd.,  Vintry  House,  Iveen  St. 
Place,  London  E.  C.  4,  England. 
McGiNNis,  F.  J.  (A) 

Box  2387,  Palm  Beach,  Fla. 
Fox  Theater,  2211  Woodward  Ave., 

Detroit,  Mich. 
McGuiRE,  PERCIVAL  A.  (M) 

International    Projector    Corp.,    90 

Gold  St.,  New  York,  N.  Y. 

Kodak  Park  Works,  Eastman  Kodak 

Co.,  Rochester,  N.  V". 
MCMATH,  R.  R.  (M) 

Motors  Metal  Mfg.  Co.,  5936  Mil- 
ford  Ave.,  Detroit,  Mich. 
McNABB,  J.  H.  (M) 

Bell  &  Howell  Co.,  1801  Larchmont 

Ave.,  Chicago,  111. 

7  Baker  Ave.,  East  Lexington,  Mass. 
McNicoL,  DONALD  (M) 

Projection  Engineering,  19  E.  47th 

St.,  New  York,  N.  Y. 
McRAE,  DONALD  (4) 

99    Melrose    St.,    Melrose,    Mass. 

Albrechtstr.,    60A,    Berlin-Sudende, 

MEES,  C.  E.  K.  (M) 

Research  Laboratories,  Eastman  Ko- 
dak Co.,  Rochester,  N.  Y. 
Mehta-Luhar  Productions,  167  Main 
Rd.,  Dadar,  Bombay,  14,  India. 

14    Brookside     Circle,     Bronxville, 

N.  Y. 

Parkstr.,  56/58,  Berlin-Dahlem,  Ger- 

Associated  Screen  News,  Ltd.,  Wes- 
tern Ave.  &  Delcarie  Blvd.,  Mon- 
treal, Que.,  Canada. 



[J.  S.  M.  p.  E. 


Agfa     Ansco     Corp.,     6370     Santa 
Monica  Blvd.,  Hollywood,  Calif. 

1788  Amsterdam  Ave.,  New  York, 

N.  Y. 

Lyon  &  Lyon,  National  City  Bank 

Bldg.,  Los  Angeles,  Calif. 

47    Westfield    Ave.,     East    Roselle 

Park.  N.  J. 

c/o  N.  V.  Philips  Co.,  Eindhoven, 


Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 

Metro-Goldwyn-Mayer  Studios,  Cul- 
ver City,  Calif. 
MISTRY,  D.  L.  (M) 

24    Nepean    Road,    Malabar    Hill, 

Bombay,  6,  India. 
MISTRY,  M.  L.  (M) 

24    Nepean    Road,    Malabar    Hill, 

Bombay,  6,  India. 

Mitchell    Camera    Corp.,    665    N. 
Robertson  Blvd.,  W.  Hollywood, 

Bell  &  Howell  Co.,  1801  Larchmont 

Ave.,  Chicago,  111. 
MOLE,  P.  (M) 

Mole-Richardson,  Inc.,  941  N.  Syca- 
more Ave.,  Hollywood,  Calif. 
MORENO,  R.  M.  (A) 

Du  Pont  Film  Mfg.  Corp.,    Parlin, 


Electrical  Research  Products,   Inc., 
7046      Hollywood      Blvd.,      Los 
Angeles,  Calif. 
MORRIS,  LLOYD  P.  (^4) 

2620   S.    Washington    St.,    Marion, 

MORTON,  H.  S.  (M) 

5650    Grand    River    Blvd.,    Grand 

River,  Mich. 

Kodak,  Ltd.,  Postafiok   146,  Buda- 
pest IV,  Hungary. 
MORTON,  WM.  M.  (A) 

R.  F.  D.  No.  7,  Knoxville,  Tenn. 
MOYSE,   HOLLIS  W.    (If) 

Smith    &    Aller,    Ltd.,    6656    Santa 
Monica  Blvd.,  Hollywood,   Calif. 

1718  N.  Sierra  Bonita,  Hollywood, 


7825  Hampson  St.,  New  Orleans,  La. 

3148  O  St.,  N.  W.,  Washington,  D.  C. 
MURRAY,  A.  P.  (A) 

14  Chilton  Road,  West  Roxbury, 


Publix  Theaters  Corp.,   Paramount 

Bldg.,  New  York,  N.  Y. 

D.  Nagase  &  Co.,  Ltd.,  Itachibori- 
Minamidori-Nishiku,       Osaka, 

National  Cash  Register  Co.,  Dayton, 

NEU,  GEORGE  H.  (A) 

Neumade  Products  Corp.,  654  Michi- 
gan Ave.,  Buffalo,  N.  Y. 
NEU,  OSCAR  F.  (A) 

Neumade   Products   Corp.,  442  W. 

42nd  St.,  New  York,  N.  Y. 

Phi  Gamma  Delta  Club,  106  W.  56th 

St.,  New  York,  N.  Y. 

Metro  -  Goldwyn  -  Mayer  Studios, 

Culver  City,  Calif. 

Kandem  Electrical,  Ltd.,  711  Ful- 
ham  Road,  London,  S.  W.  6,  Eng- 

Feb.,  1933] 



NIXON,  IVAN  L.  (M) 

Bausch  &  Lomb  Optical  Co., 
Rochester,  N.  Y. 


Friedrich    Karl-Ufer  2/4,    Berlin, 
N.  W.  40,  Germany. 
NORLING,  J.  A.  (M) 

Loucks  &  Norling,  245  W.  55th  St., 

New  York,  N.  Y. 
NORRISH,  B.  E  .(M) 

Associated  Screen  News  of  Canada, 
Ltd.,  Western  Ave.  &  Delcarie 
Blvd.,  Montreal,  Que.,  Canada. 


Du  Pont  Film  Mfg.  Co.,  Parlin,  N.  J. 

Eastman  Kodak  Co.,  24  Yuen  Ming 

Yuen  Road,  Shanghai,  China. 

Warner  Bros.    Pictures,   Inc.,    1277 

E.  14th  St.,  Brooklyn.  N.  Y. 

National  Theater  Supply  Co.,  2310 

Cass  Ave.,  Detroit,  Mich. 

"Poole,"  Shakespeare  Rd.,  Mill  Hill, 

London,  N.  W.  7,  England. 

J.   Osawa  &  Co.,   Ltd.,   Sanjo  Ko- 

bashi,  Kyoto,  Japan. 
OSBORNE,  A.  W.  (4) 

"Hilton"     North     Drive,     Ruislip, 

Middlesex,  England. 
OSTER,  E.  (A) 

5070    Woodley    Ave.,    Van    Nuys, 


2089    E.    Mountain    St.,    Pasadena, 

OTT,  HARRY  G.  (M) 

Spencer    Lens    Co.,    19    Doat    St., 

Buffalo,  N.  Y. 

2647  Broadway,  New  York,  N.  Y. 

PACENT,   Louis  G.    (M) 

Pacent      Reproducer      Corp.,      91 
Seventh  Ave.,  New  York,  N.  Y. 
PAGE,  Louis  I.   (A) 
RKO  Studios,  Inc.,  780  Gower  St., 

Hollywood,    Calif. 
PALMER,  M.  W.  (M) 

Motion  Picture  Lighting  Co.,  34-12 
Graham  Ave.,  Long  Island  City, 
N.  Y. 

Berk  House,  76  William  St.,  Sydney, 

N.  S.  W.,  Australia. 

Pacent  Electric  Co.,  91  Seventh  Ave., 

New  York,  N.  Y. 

Studio  Film  Laboratories,  Ltd.,  80 

Wardour  St.,  London,  England. 

University      Theater,      Cambridge, 


Krishna  &  Gujrat  Studios,  162  Dadar 

Rd.,  Dadar,  Bombay,  India. 

Ontario  Govt.  M.  P.  Bureau,  Parlia- 
ment Bldgs.,  Toronto,  Ont.,  Can. 
PECK,  W.  H.  (A) 

5  Forest  Lane,  Scarsdale,  N.  Y. 
PETERSON,  F.  W.  (M) 

I.  G.  Farbenindustrie  Aktiengesell- 
schaft,  Kinotechnische  Abteilung, 
Berlin,  S.  O.  36,  Germany. 
PETTENGILL,    GEORGE    W.,    JR.     (4) 
Motion    Picture    Service    Co.,    735 
Arlington  Ave.,  N.  St.  Petersburg, 

1240  N.  Bath  Ave.,  Oklahoma  City, 

PHELPS,  L.  G.   (M) 

Phelps-Films,  Inc.,  126  Meadow  St., 

New  Haven,   Conn. 
PHILLIMORE,  C.  E.  (4) 

707  Home  Ave.,  Oak  Park,  111. 

1455  Gordon  St.,  Hollywood,  Calif. 



[J.  S.  M.  P.  E. 

PIERCE,  ROBT.  H.  (^4) 
4538  Denny  Ave.f   N.   Hollywood, 


513   N.  Lucerne  Blvd.,   Hollywood, 


61  Pleasant  St.,  Brookline,  Mass. 

142  Camden  Road,  London,  N.  W.  1, 


1626   N.    Crescent   Heights,    Holly- 
wood, Calif. 

2975  Marion  Ave.,  Bronx,  N.  Y. 
PORTER,  C.  D.  (4) 

Publix  Theaters  Corp.,  57  Ellis  St., 

N.  E.,  Atlanta,  Ga. 

Engr.  Dept.,  General  Electric  Co., 

Nela  Park,  Cleveland,  Ohio. 
POTE,  ALFRED  J.  04) 

270  Chestnut  St.,  Chelsea,  Mass. 
PRESIDENT,  THE  (Honorary) 

Die  Deutsche  Kinotechnische  Gesell- 
schaft,   Berlinerstr.,    172,   Berlin- 
Charlottenburg,  Germany. 
PRESIDENT,  THE  (Honorary) 
Royal    Photographic    Society,     35 
Russell  Square,  London,  W.  C.  1. 

PRESIDENT,  THE  (Honorary) 
Societe  Francaise  de  Photographic, 
51  Rue  de  Clichy,  Paris,  France. 
Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 
Pu,  MAUNG  NYI  (.4) 
Burmese    Favourite    Co.,    51    Sule 
Pagoda  Road,  Rangoon,  Burma, 


Fox  Film  Corp.,  1401  Northwestern 
Ave.,  Hollywood,  Calif. 


M.  Rabinowitz  &  Sons,  Inc.,  1373 
Sixth   Ave.,    New   York,    N.    Y. 

Technicolor  Motion  Picture  Corp., 
823   N.   Seward  St.,  Hollywood, 

Motion  Picture  Herald,  1790  Broad- 
way, New  York,  N.  Y. 

Geo.  Washington  Hotel,  Lexington 
Ave.  and  23rd    St.,   New  York, 
N.  Y. 

458  Archer  St.,  Freeport,  L.  I.,  N.  Y. 
RAVEN,  A.  L.  (M) 

Raven  Screen  Corp.,  147  E.  24th  St., 

New  York,  N.  Y. 
RAY,  REID  H.  (M) 

Ray-Bell  Films,  Inc.,  817  University 

Ave.,  St.  Paul,  Minn. 

Bausch     &     Lomb     Optical     Co., 

Rochester,  N.  Y. 
READ,  EARL  A.  (-4) 

1125  Cleveland  Ave.,  N.  W.,  Canton, 


The    Unicorn    Hotel,    Altringham, 

Cheshire,  England. 
REDPATH,  WM.    (M) 

156  King  St.,  W.  Toronto,  Ont.,  Can. 
REEB,  OTTO  G.  L.  (A) 

Rotherstr.,  20-23,  Berlin  O.  17,  Ger- 

Hollywood  Motion  Picture  Equip- 
ment Co.,  Ltd.,  6416  Selma  Ave., 
Hollywood,  Calif. 

RCA  Victor  Co.,  Camden,  N.  J. 
REISMAN,  P.  H.  (M) 
362    Pelham    Rd.,    New    Rochelle, 

N.  Y. 

Renier  Mfg.    Co.,   2216  State  St., 
Milwaukee,  Wis. 

Feb.,  1933] 



RENWICK,  F.  F.  (4) 

Ilford,  Ltd.,  Ilford,  Essex,  England. 
REPP,  WILLIAM  H.  (4) 

Projection    Optics    Co.,    330  Lyell 

Ave.,  Rochester,  N.  Y. 
RICHARD,  A.  P,  (A) 
97   Rue    Lemercier,    Paris,    XVII, 


Mole-Richardson,  Inc.,  941  N.  Syca- 
more Ave.,  Hollywood,  Calif. 

3  Tudor  Lane,  Scarsdale,  N.  Y. 

39-41  58th  St.,  Woodside,  L.  I.,  N.  Y. 
RICKS,  HUBERT  M.  (.4) 

Weston  Electrical  Instrument  Corp., 
614  Frelinghuysen  Ave.,  Newark, 
RIDER,  JOHN  F.  (M) 

1440  Broadway,  New  York,  N.  Y. 
RINALDY,  E.  S.  (A) 

Chester,  N.  J. 
RIPLEY,  PAUL  L.  (4) 

Warner  Bros.   Pictures,   Inc.,    1277 

E.  14th  St.,  New  York,  N.  Y 
ROGALLI,  N.  J.  (A) 

2753  Cruger  Ave.,  Bronx,  N.  Y. 

"Cluny,"  Deacons  Hill  Road,   Els- 
tree,  Herts,  England. 

Bausch  &  Lomb  Optical  Co.,   1401 

S.  Hope  St.,  Los  Angeles,  Calif. 
Ilex  Optical  Co.,  726  Portland  Ave., 

Rochester,  N.  Y. 

Kodak  A.-G.,  Markgrafenstr.,  7-6, 
Berlin,  Germany. 


Rockefeller    Institute,    66th    St.    & 

York  Ave.,  New  York,  N.  Y. 

H.  E.  R.  Laboratories,  Inc.,  457 
W.  46th  St.,  New  York, 
N.  Y. 


Zimmerstr.,  35,  Berlin,  S.  W.  68,  Ger- 
Ross,  CHARLES  (A) 

Motion    Picture    Service    Co.,    318 
W.  48th  St.,  New  York,  N.  Y. 
Ross,  ERNEST  (M) 

United  Research  Corp.,  41-39  38th 

St.,  Long  Island  City,  N.  Y. 
Ross,  O.  A.  (M) 

198    Broadway,    Room    903,    New 
York,  N.  Y. 


Globe  Theater,  Boston,  Mass. 
ROUSE,  J.  J.  (A) 

Kodak  Australasia  Ptg.,  Ltd.,  379 
George  St.,   Sydney,   N.   S.   W., 

76    Wardour    St.,    London,    W.    1, 


Paramount  Publix  Corp.,  Paramount 

Bldg.,  New  York,  N.  Y. 

Paramount  Publix  Corp.,  5451  Mara- 
thon St.,  Hollywood,  Calif. 

Kodak,    Ltd.,    Kingsway,    London, 

E.  C.  2,  England. 

Hall  &  Connolly,  Inc.,  24  Van  Dam 

St.,  New  York,  N.  Y. 

7937  S.  Wood  St.,  Chicago,  111. 

Paramount  Publix  Corp.,  5451  Mara- 
thon St.,  Hollywood,  Calif. 


Riverbank  Laboratories,  Geneva,  111. 

Automatic  Devices  Co.,  737  Hamil- 
ton St.,  Allentown,  Pa. 

Research  Laboratories,  Eastman  Ko- 
dak Co.,  Rochester,  N.  Y. 



[J.  S.  M.  P.  E. 


140-31  58th  Road,  Flushing,  L.  I., 

N.  Y. 

Electrical  Research  Products,  Inc., 
250  W.  57th  St.,  New  York,  N.  Y. 

SCHAEFFER,   JOHN   M.    (-4) 

1003  Dobson  St.,  Evanston,  111. 


429  Maple  Ave.,  Westmont,  N.  J. 

401    W.    Washington    Blvd.,    Fort 
Wayne,  Indiana. 


101  Park  Ave.,  New  York,  N.  Y. 

C.  P.  Goerz  American  Optical  Co., 
317    E.    34th    St.,    New    York, 
N.  Y. 

Agfa    Ansco     Corp.,     Binghamton, 

N.  Y. 

Kodak    Co.,    39    Ave.    Montaigne, 

Paris,  France. 

Getreidemarkt,  9,  Vienna,  IV,  Aus- 

School  of  Medicine,   University  of 
Rochester,    Crittenden    Blvd., 
Rochester,  N.  Y. 

Columbus  Industrial  Film  Co.,  150 
S.  Third  St.,  Columbus,  Ohio. 


34-14     Parsons     Blvd.,     Flushing, 

L.  I.,  N.  Y. 

Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 

Du  Pont  Film  Mfg.  Co.,  Parlin,  N.  J. 

Moviola    Co.,     1451     Gordon    St., 
Hollywood,  Calif. 


Rialto    Theater,    West   25th  St.  & 
Bridge    Ave.,     Cleveland,     Ohio. 

147  Cooper  Ave.,  Peoria,  111. 
SHAMRAY,  P.  L.  (M) 

Smith    &    Aller,    Inc.,    6656    Santa 
Monica  Blvd.,  Hollywood,  Calif. 
SHAPIRO,  A.  (M) 

Universal    Stamping    &    Mfg.    Co., 
2839  Northwestern  Ave.,  Chicago, 

Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 

Research  Laboratories,  Eastman  Ko- 
dak Co.,  Rochester,  N.  Y. 
SHERIDAN,  P.  T.  (A) 

Electrical  Research  Products,   Inc., 
250  W.  57th  St.,  New  York,  N.  Y. 
SHIMEK,  JOHN  A.  (.4) 

2207  Byron  St.,  Chicago,  111. 
SHIRAS,  ANNE  (.4) 

841  Ellsworth  Ave.,  Pittsburgh,  Pa. 
SHOTWELL,  H.  H.  (A) 

32  N.  Worth  St.,  Elgin,  111. 
SHULTZ,  E.  PAT  (A) 

1016  N.  Sycamore  Ave.,  Hollywood, 


Electrical  Research  Products,  Inc., 
7046      Hollywood      Blvd.,      Los 
Angeles,    Calif. 
SKITTRELL,  J.  Y.  (10 

Olympic     Kinematograph     Labora- 
tories, School  Road,  London,  W. 
10,  England. 
SLOAN,  JAMES  B.  (4) 

4,  The    Avenue,     Bedford     Park, 
London,   W.   4,   England. 

SMACK,  JOHN  C.  (4) 

5.  S.  White  Dental  Mfg.  Co.,   152 
W.  42nd  St.,  New  York,  N.  Y. 

SMITH,  J.  E.  (M) 

National   Radio   Institute,    16th   & 
U  Sts.,  N.  W.,  Washington,  D.  C. 

Feb.,  1933] 



SMITH,  J.  W.  (A) 

23  Purley  Ave.,   Cricklewood,  Lon- 
don, N.  W.  2,  England. 

P.  O.  Box  245,  Ottawa,  Ont.,  Canada. 
SPAHR,  ORAL  F.  (M) 

4431  W.  Lake  St.,  Chicago,  111. 
SPENCE,  JOHN.  L.,  JR.  (M) 

Akeley  Camera,  Inc.,  175  Varick  St., 

New  York,  N.  Y. 

277  Park  Ave.,  New  York,  N.  Y. 

Warner  Bros.  Pictures,  Inc.,  1277  E. 

14th  St.,  Brooklyn,  N.  Y. 
STAFFORD,  J.  W.  (A) 

l237l/2  N.  Ogden  Drive,  Hollywood, 


P.  O.  Box  418,  Cleveland,  Ohio. 

Bell  &  Howell  Co.,  1801  Larchmont 

Ave.,  Chicago,  111. 

41     Watsessing     Ave.,     Bloomfield, 


S.  M.   Chemical  Co.,  Inc.,  514  W. 

57th  St.,  New  York,  N.  Y. 
STEWART,  GEO.  E.  (M) 

40  Hillside  Ave.,  Rockville  Center, 

L.  I.,  N.  Y. 
STOLLER,  H.  M.  (M) 

Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 
Jenkins   &  Adair,   Inc.,   3333   Bel- 

mont  Ave.,  Chicago,  111. 

4549  193rd  St.,  Flushing,  L.  I.,  N.  Y. 
STRICKLER,  J.  F.  (4) 

Jam    Handy    Picture    Corp.,    2900 
E.   Grand  Blvd.,    Detroit,   Mich. 

Strong  Electric  Co.,  2501  LaGrange 
St.,  Toledo,  Ohio. 


1343  N.  Orange  Grove  Ave.,  Holly- 
wood, Calif. 

American  Askania  Corp.,  809  M.  & 

M.  Bldg.,  Houston,  Texas. 
Shree  Ranjit  Film  Co.,  Dadar  Main 
Road,     Dadar,     Bombay,     India. 


R.  Konishi   &   Co.,   18  Honcho,  2- 
Chome,     Nihonbashiku,     Tokyo, 

University      Theater,      Cambridge, 


RCA  Victor  Co.,  Camden,  N.  J. 
SWAAB,  M.  L.  (A} 

5038  Chestnut  St.,  Philadelphia,  Pa. 
SWARTZ,  E.  M.  (A) 

Keystone    Mfg.     Co..    288    A    St., 

Boston,  Mass. 

306  Ldwell  St.,  Manchester,  N.  H. 


United  Research  Corp.,  41-39  38th 

St.,  Long  Island  City,  N.  Y. 

General  Electric  Co.,  Schenectady, 

N.  Y. 

Protecto  Films,  Inc.,  105  W.  40th  St.. 

New  York,  N.Y. 

Geo.  Humphries  &  Co.,   10  North- 
court,     Chitty     St.,     Tottenham 
Court  Rd.,   London,  W.  1,  Eng- 
TERRY,  ROY  V.  (M) 

Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 
THAYER,  WM.  L.  (4) 

Paramount  Publix  Corp.,  5451  Mara- 
thon  St.,   Hollywood,    Calif. 



[J.  S.  M.  P.  E. 


508  S.   Union  Drive,   Los  Angeles, 


35  Linden  Ave.,   Metuchen,   N.   J. 

352  S.  Drexel  Ave.,  Detroit,  Mich. 

Wm.    H.    Bristol   Talking    Pictures 

Corp.,  Waterbury,  Conn. 

Tiltz  Engineering  Co.,  480  Lexing- 
ton Ave.,   New  York,   N.   Y. 

First    National    Pathe,    Ltd.,     103 
Wardour  St.,  London,  W.  1,  Eng- 

125    Merchants    Road,    Rochester, 

N.  Y. 

Consolidated  Film  Industries,  Inc., 
1776  Broadway,  New  York,  N.  Y. 

Consolidated  Film  Industries,   Inc., 
203  W.  146th  St.,  New  York,  N.  Y. 
TsucHmAsm,  HARUO  (.4) 

88  Shimpoin-cho,  Tenneji-ku,  Osaka, 

TUCKER.  Louis  B.  04) 

Tucker  Picture  Co.,  25  Sackville  St., 
Port  of  Spain,  Trinidad,  British 
West  Indies. 

H.  E.  R.  Laboratories,  Inc.,  437  W. 

46th  St.,  New  York,  N.  Y. 
Research  Laboratories,  Eastman  Ko- 
dak Co.,  Rochester,  N.  Y. 
TUTTLE,  H.  B.  (M) 

Eastman    Kodak    Co.,    343    State 
Street,  Rochester,  N.  Y. 

UNDERBILL,  Jos.  L.  04) 

RCA  Photophone,  Ltd.,  Film  House, 
Wardour  St.,  London,  England. 


Filmcraft    Labs.,    35-39   Missenden 
Rd.,    Camperdown,  Sydney,  Aus- 

Via  Emanuele  Filiberto,  100,  Rome, 

VICTOR,  A.  F.  (M) 

Victor  Animatograph  Co.,  242  W. 

55th  St.,  New  York,  N.  Y. 

6627  Emmett  Terrace,   Hollywood, 

VOLTAM,  WM.  J.  (A) 

71  Piermont  St.,  Wollaston,  Mass. 


Warner  Bros.  Pictures,  Inc.,  1277  E. 

14th  St.,  Brooklyn,  N.  Y. 
WADDINGHAM,  A.  G.   (M) 

PhotocolorCorp.,  Irvington-on-Hud- 

son,  N.  Y. 

General  Pictures,   Inc.,  43-77  Ver- 
non    Ave.,     Long     Island     City, 
N.  Y. 
WALL,  JOHN  M.  (M) 

J.  M.  Wall  Machine  Co.,  101  Court 

St.,  Syracuse,  N.  Y. 

R.  F.  D.  No.  3,  Huntington,  L.  I., 

N.  Y. 
WARD,  ERWIN  J.  04) 

553  De  Nise  Road,  Rochester,  N.  Y. 

Bell  &  Howell  Co.,  4045  N.  Rock- 
well St.,  Chicago,  111. 

Aktiengesellschaft    fur     Film    Fab- 
rikation,  Victoriastr.,  13/18,  Ber- 
lin-Tempelhof,    Germany. 

Western  Electric  Co.,  Bush  House, 
Aldwych,  London,  W.  C.  2,  Eng- 
WATSON,  J.  S.,  JR.  04) 

6   Sibley   Place,    Rochester,    N.    Y. 

Feb.,  1933] 



WEBB,  H.  W.  (M) 

211  Glenwood  Ave.,  Leonia,  N.  J. 
WEBER,  CARL  M.  (M) 
Weber  Machine  Corp.,   55  Bengal 

Terrace,  Rochester,  N.  Y. 
207      Finance      Bldg.,      Cleveland, 


Bell    Telephone    Laboratories,    463 

West  St.,  New  York,  N.  Y. 

Warner  Bros.  Pictures,  Inc.,  1277  E. 

14th  St.,  Brooklyn,  N.  Y. 

Research  Laboratories,  Eastman  Ko- 
dak Co.,  Rochester,  N.  Y. 
WHITE,  D.  R.  (M) 

Du   Pont   Film   Mfg.    Co.,    Parlin, 


WmTMORE,  WILL  (^4) 
Western    Electric    Co.    50    Church 

St.,  New  York,  N.  Y. 

22  Rue  Cambaceres,  'Paris,    VIII, 


7635    Grand    River    Blvd.,    Grand 

River,  Mich. 
WILDUNG,  F.  H.  (A) 

1920  S  St.,  Washington,  D.  C. 

RCA  Photophone,  Inc.,  c/o  Inter- 
national   General    Electric    Co., 
Stephen  House,  Dalhousie  Square, 
Calcutta,  India. 
WILLIFORD,  E.  A.  (M) 

National    Carbon    Co.,    Box    400, 

Cleveland,  Ohio. 

5657  Sunset  Blvd.,  Hollywood,  Calif. 

72    Penryhn    Ave.,    Walthamstow, 

London,  E.  17,  England. 

12  Whitehall  Rd.,  Harrow,  Middle- 
sex, England. 

WINN,    CURTIS   B.,   JR.    (A) 
421  E.  J  St.,  Ontario,  Calif. 


Topical  Film  Co.,  Brent  Laborato- 
ries, Ltd.,  North  Circular  Road, 
London,  N.  W.  2,  England. 

8970  Kelson  Ave.,  Los  Angeles,  Calif. 
WOLF,  SIDNEY  K.  (4) 

Electrical  Research  Products,  Inc., 
250  West  57th  St.,  New  York.  N.Y. 
Weston  Electrical  Instrument  Corp., 

Newark,  N.  J. 
WOODS,  FRANK  E.   (M) 

Academy  M.  P.  Arts  &  Sciences, 
7046  Hollywood  Blvd.,  Hollywood, 

WORSTELL,  R.  E.   (4) 

General  Electric  Co.,  Nela  Park, 
Cleveland,  Ohio. 

YAGER,  GEORGE  A.  (4) 

167  N.  W.  Temple  St.,  Salt  Lake 

City,  Utah. 
YAGER,  H.  BARTON  (^4) 

61  Morton  St.,  New  York,  N.  Y. 
YATES,  E.  C.  (A) 

Capitol  Theater,  Singapore,  Straits 

YOUNG,  AL  (M) 

Du-Art  Film  Laboratories,  Inc., 
245  W.  55th  St.,  New  York,  N.  Y. 

ZERK,  OSCAR  U.  (M) 

3206  Palmolive  Bldg.,  Chicago,  111. 
ZIEBARTH,  C.  A.  (If) 

Bell  &  Howell  Co.,  1801  Larchmont 

Ave.,  Chicago,  111. 
ZOELTSCH,  W.  F.  (A) 

461  Central  Ave.,  Union  City,  N.  J. 
ZUBER,  JOHN  G.  (A) 

Bell  &  Howell  Co.,  1801  Larchmont 

Ave.,  Chicago,  111. 

700  W.  175th  St.,  New  York,  N.  Y. 


Photocells  and  Their  Application.  V.  K.  ZWORYKIN  AND  E.  D.  WILSON. 
John  Wiley  and  Sons,  New  York,  N.  Y.,  Second  Edition,  1932,  xv  +  331  pp. 
(180  Figures).  $3.00.  This  book  is  an  extensive  revision  of  the  former  edition 
published  in  1930.  More  than  one  hundred  and  twenty  pages  have  been  added, 
by  including  five  new  chapters  and  adding  considerably  to  the  existing  chapters. 
Important  new  data  have  been  interspersed  throughout  the  text,  the  value  of 
the  book  thus  being  considerably  enhanced  for  the  average  reader. 

Works  on  photoelectricity  seem  prone  to  one  of  two  extremes.  Either  so 
much  information  is  omitted  that  the  book  seems  sketchy  and  of  limited  value, 
or  so  much  detail  is  incorporated  that  reading  becomes  difficult  unless  one  is  an 
authority  on  the  subject.  It  seems  to  the  reviewer  that  the  authors  have  avoided 
both  extremes  in  the  second  edition  and  have  produced  a  work  that  is  very 
readable  in  addition  to  its  being  useful  for  consultation  with  its  very  complete 
references  and  bibliography. 

This  edition  follows  the  same  general  arrangement  as  the  previous  one.  The 
first  two  chapters  on  history  and  general  theory  are  substantially  unchanged. 
The  third  chapter  on  photosensitive  films  is  new  and  constitutes  a  short  resume 
of  this  important  subject.  The  next  two  chapters  describe  the  materials  and 
apparatus  used  and  the  technic  followed  in  constructing  the  vacuum  and  gas- 
filled  cells  whose  characteristics  are  described  in  the  succeeding  two  chapters. 
Photoconduction  and  photovoltaic  cells  are  treated  much  more  fully  than  in 
the  previous  edition,  where  they  were  limited  to  one  short  chapter,  now  expanded 
into  two.  The  new  dry  or  sperrschicht  cells,  which  have  attracted  so  much 
attention  recently,  are  discussed  under  the  subject  of  voltaic  cells.  The  three 
chapters,  ten  to  twelve,  lead  the  reader  from  considerations  of  photo-output  and 
amplifying  tubes  and  the  optimum  output  of  various  types  of  cells,  through  the 
problem  of  amplification  and  carrier  modulation  by  various  means.  The  re- 
maining seven  chapters  constitute  a  comprehensive  review  of  such  applications 
as  special  light-sensitive  devices,  photometry  and  colorimetry,  sound  movies, 
facsimile  transmission,  television,  miscellaneous  uses,  and  probable  future  ad- 
vancement. E.  F.  KINGSBURY 





A.  N.  GOLDSMITH,  570  Lexington  Ave.,  New  York,  N.  Y. 

J.  I.  CRABTREE,  Eastman  Kodak  Company,  Rochester,  N.  Y. 


E.  I.  SPONABLE,  Fox  Film  Corp.,  New  York,  N.  Y. 
W.  C.  KUNZMANN,  National  Carbon  Co.,  Cleveland,  Ohio. 

J.   H.   KURLANDER,   Westinghouse  Lamp  Co.,   Bloomfield,  N.  J. 

H.  T.  COWLING,  Rochester,  N.  Y. 

Board  of  Governors 

H.  T.  COWLING,   311  Alexander  St.,  Rochester,  N.  Y. 

J.  I.  CRABTREE,  Research  Laboratories,  Eastman  Kodak  Co.,  Rochester,  N.  Y. 

P.  H.  EVANS,  Warner  Bros.  Pictures,  Inc.,  1277  E.  14th  St.,  Brooklyn,  N.  Y. 

R.  E.  FARNHAM,  General  Electric  Co.,  Nela  Park,  Cleveland,  Ohio. 

O.  M.  GLUNT,  Bell  Telephone  Laboratories,  Inc.,  New  York,  N.  Y. 

A.  N.  GOLDSMITH,  570  Lexington  Ave.,  New  York,  N.  Y. 

W.  C.  HUBBARD,  General  Electric  Vapor  Lamp  Co.,  Hoboken,  N.  J. 

R.  F.  MITCHELL,  Bell  &  Howell  Co.,  1801  Larchmont  Ave.,  Chicago,  111. 

J.  H.  KURLANDER,  Westinghouse  Lamp  Co.,  Bloomfield,  N.  J. 

W.  C.  KUNZMANN,  National  Carbon  Co.,  Cleveland,  Ohio. 

E.  HUSE,  Eastman  Kodak  Co.,  6706  Santa  Monica  Ave.,  Hollywood,  Calif. 

L.  C.  PORTER,  General  Electric  Co.,  Nela  Park,  Cleveland.  Ohio. 

E.  I.  SPONABLE,  Fox  Film  Corp.,  850  Tenth  Ave.,  New  York.  N.  Y. 




[J.  S.  M.  p.  E. 


R.  M.  EVANS 

P.  D.  BREWSTER,  Chairman 


N.  M.  LA  PORTE 



W.  C.  KUNZMANN,  Chairman 




Development  and  Care  of  Film 
R.  F.  NICHOLSON,  Chairman 

A.  Hi  ATT 






V.  B.  SEASE 
J.  H.  SPRAY 

O.  B.  DEPUE 

C.  L.  GREGORY,  Chairman 




B.  W.  DEPUE 

C.  D.  ELMS 

E.  R.  GEIB 


B.  W.  DEPUE 
O.  B.  DEPUE 


Membership  and  Subscription 

H.  T.  COWLING,  Chairman 
W.  H.  CARSON,  Vice- Chairman 

J.  G.  T.  GILMOUR 
E.  E.  LAMB 

E.  THEISEN,  Chairman 

W.  V.  D.  KELLEY 



Feb.,  1933] 



A.  A.  COOK 
W.  B.  COOK 
H.  A.  DEVRY 

Non-Theatrical  Equipment 
R.  E.  FARNHAM,  Chairman 

E.  R.  GEIB 
N.  B.  GREEN 
L.  A.  JONES 


R.  P.  MAY 



P.  H.  EVANS 
A.  C.  HARDY 

O.  M.  GLUNT,  Chairman 


P.  A.  McGuiRE 
D.  McNicoL 

T.  E.  SHEA 


Preservation  of  Film 
W.  H.  CARSON,  Chairman 




V.  B.  SEASE 


A.  A.  COOK 



J.  G.  FRAYNE,  Chairman 

F.  S.  IRBY 
E.  E.  LAMB 

S.  S.  A.  WATKINS 

J.  O.  BAKER 
J.  J.  FINN 

Projection  Practice 
H.  RUBIN,  Chairman 



P.  A.  McGuiRE 



E.  R.  GEIB 

Projection  Screens 
S.  K.  WOLF,  Chairman 

A.  L.  RAVEN 




H.  P.  GAGE 

Projection  Theory 
A.  C.  HARDY,  Chairman 


B.  W.  DEPUE 

W.  WHITMORE,  Chairman 

F.  S.  IRBY 


D.  McNicoL 

P.  H.  EVANS 
N.  M.  LA  PORTE 

H.  B.  SANTEE,  Chairman 


W.  A.  MACNA1R 

S.  K.  WOLF 

L.  E.  CLARK 
P.  H.  EVANS 

Standards  and  Nomenclature 
M.  C.  BATSEL,  Chairman 

A.  C.  HARDY 
L.  A.  JONES 
N.  M.  LA  PORTE 

V.  B.  SEASE 
T.  E.  SHEA 
S.  K.  WOLF 



Studio  Lighting 

P.  MOLE,  Chairman 

R.  F.  MITCHELL,  Chairman 
B.  W.  DEPUE,  Sec.-Treas. 

Chicago  Section 


O.  B.  DEPUE,  Manager 
J.  E.  JENKINS,  Manager 

New  York  Section 

P.  H.  EVANS,  Chairman 

D.  E.  HYNDMAN,  Sec.-Treas. 

Pacific  Coast  Section 

EMERY  HUSE,  Chairman 
G.  F.  RACKETT,  Sec.-Treas. 

M.  C.  BATSEL,  Manager 
J.  L.  SPENCE,  Manager 

C.  DREHER,  Manager 
J.  A.  DUBRAY,  Manager 



At  a  meeting  held  at  the  Hotel  Sagamore,  Rochester,  N.  Y.,  January  20,  Mr. 
L.  C.  Porter,  who  held  the  office  of  President  of  the  Society  during  1922,  1923, 
and  1929,  and  various  other  offices  since  1917,  tendered  his  resignation  as  a  mem- 
ber of  the  Board.  Mr.  H.  Griffin  was  appointed  to  serve  in  his  stead  until  the  ex- 
piration of  his  term  of  office. 

Extensive  discussion  concerning  the  approaching  convention  to  be  held  April 
24  to  28,  resulted  in  conclusions  described  below  under  the  heading  Spring,  1933, 
Convention.  Considerable  attention  was  given  by  the  Board  to  budgetary  mat- 
ters, including  sectional  and  committee  appropriations,  to  the  question  of  dues 
and  subscriptions,  and  to  the  general  relation  between  the  prevailing  economic 
conditions  and  the  finances  of  the  Society.  In  order  to  assist  in  distributing  the 
JOURNAL  among  subscribers,  a  special  plan  was  devised,  offering  to  the  first  one 
hundred  individuals  to  take  advantage  of  the  plan,  complete  issues  of  back  num- 
bers of  the  JOURNAL.  Thus,  by  subscribing  for  the  JOURNAL  for  1933  and  1934,  at 
a  cost  of  twenty-four  dollars,  the  first  one  hundred  such  subscribers  will  be  en- 
titled to  receive  a  complete  set  of  JOURNALS  for  1930  and  1931,  without  further 
payment  except  for  postage  or  expressage.  This  offer  is  open  also  to  present  sub- 
scribers who  might  wish  to  extend  their  subscriptions. 

Recommendations  made  by  the  S.  M.  P.  E.  Historical  Committee  concerning 
the  requirements  for  honorary  membership  were  submitted  to  the  Board .  These 
requirements,  after  further  study,  will  receive  final  action  at  the  next  meeting  of 
the  Board,  to  be  held  on  April  23  at  New  York,  N.  Y. 

The  Board  was  notified  of  the  formation  of  two  new  motion  picture  societies, 
namely,  the  Motion  Picture  Society  of  India,  and  the  Magyar  Kinotechnikai 
Tarsasag.  The  Society  extends  to  these  new  organizations  its  best  wishes  for  success. 

Action  was  taken  by  the  Board  on  the  report  of  the  Committee  on  Standards 
and  Nomenclature,  published  in  the  November,  1932,  issue  of  the  JOURNAL,  as 
described  below  under  the  heading  Standards. 

April  24-28,  inclusive;  New  York,  N.  Y. 

At  the  meeting  of  the  Board  of  Governors  held  on  October  5  at  New  York, 
plans  for  the  Spring,  1933,  Convention  were  initiated:  the  meeting  is  to  be  held 
at  New  York,  N.  Y.,  and  of  five  days'  duration — April  24  to  28,  inclusive. 

Mr.  W.  C.  Kunzmann,  chairman  of  the  Convention  Committee,  assisted  by 
Mr.  H.  Griffin,  chairman  of  the  Local  Arrangements  Committee,  is  proceeding 
with  arrangements  to  hold  the  Convention  at  the  Hotel  Pennsylvania,  in  the 
Salle  Moderne. 

Mr.  O.  M.  Glunt,  chairman  of  the  Papers  Committee,  promises  an  extremely 
interesting  schedule  of  papers;  the  number  of  papers  to  be  presented  will  be 


178  SOCIETY  ANNOUNCEMENTS  [j.  S.  M.  p.  E. 

limited  to  what  can  be  accommodated  in  the  allotted  time  without  haste  or  crowd- 
ing, a  feature  that  will  assist  considerably  in  the  selection  of  papers  from  the  point 
of  view  of  technical  quality,  with  less  emphasis  on  quantity.  At  the  meeting  of 
the  Board  of  Governors  on  January  20,  Mr.  Glunt  presented  a  tentative  draft  of 
a  proposed  papers  program  for  the  Spring  Convention,  which,  in  its  general  form 
and  with  suitable  recommendations,  was  approved  by  the  Board.  At  a  meeting 
of  the  Papers  Committee  to  be  held  in  the  near  future,  the  proposed  program 
will  be  put  into  a  more  final  form,  prior  to  its  being  mailed  to  the  membership 
of  the  Society. 

An  exhibit  of  newly  developed  motion  picture  equipment  will  be  held,  as  at 
past  Conventions,  which  should  prove  of  considerable  interest  to  every  one 
interested  in  motion  picture  engineering.  Manufacturers  of  equipment  are 
invited  to  communicate  with  the  General  Office  of  the  Society,  33  W.  42nd  St., 
New  York,  N.  Y.,  for  information  regarding  the  regulations  of  the  exhibit  and 
arrangements  for  space.  Charges  for  space  will  be  made  according  to  the  size  of 
each  exhibit  and  the  space  occupied  by  it. 

Plans  are  being  made  to  assist  out-of-town  visitors  to  the  Convention  to  pass 
an  interesting  time  while  in  New  York,  and  special  film  programs  and  trips  of 
interest  will  be  arranged  for.  Full  details  of  the  program,  including  hotel  rates 
and  other  pertinent  information  will  be  mailed  to  the  members  of  the  Society  at  a 
later  date.  Members  and  friends  of  the  Society  are  urged  to  make  every  effort  to 
attend  the  Convention. 


At  the  meeting  of  the  Board  of  Governors  on  January  20,  the  report  of  the 
Standards  and  Nomenclature  Committee,  published  in  the  November,  1932, 
issue  of  the  JOURNAL,  was  accepted.  In  particular,  by  separate  action,  the  recom- 
mendations made  in  that  report,  dealing  both  with  35-  and  16-mm.  film,  were 
adopted  as  motion  picture  standards  to  be  recommended  to  the  American  Stand- 
ards Association,  in  the  requisite  form,  for  its  approval. 


At  the  December  meeting  of  the  Chicago  Section,  held  at  the  plant  of  Jenkins 
&  Adair,  Inc.,  Mr.  J.  E.  Jenkins  described  the  new  Phonopticon,  a  lantern-slide 
projector  employ  ing  disk  records  for  sound  accompaniment,  and  the  Controllo- 
phone,  an  automatic  sound  reproducer  and  equipment  demonstrator.  A  new 
35-mm.  portable  sound-on-film  recorder  was  also  demonstrated.  At  the  January 
meeting,  the  preliminary  report  of  the  Sub-committee  on  Laboratory  Practices, 
of  the  Committee  on  the  Care  and  Development  of  Film,  was  read  by  Mr.  R.  F. 
Mitchell,  chairman,  and  carefully  discussed  by  all  those  present. 


A  meeting  of  this  Committee  was  held  at  New  York,  N.  Y.,  on  January  18.  The 
Committee  is  at  the  present  time  engaged  in  the  study  of  screen  illumination,  and 
is  making  a  series  of  measurements  in  a  number  of  theaters  that  are  expected  to 
furnish  data  representative  of  the  general  conditions  existing.  Another  matter 
upon  which  the  Committee  is  placing  great  emphasis  is  the  question  of  inducing 
producers  to  review  releases  under  conditions  of  illumination  comparable  with 

Feb.,  1933]  SOCIETY  ANNOUNCEMENTS  179 

those  found  in  the  theaters,  so  that  prints,  when  projected  in  theaters,  will  not  be 
found  too  dense  to  permit  adequate  screen  illumination,  although  they  may  have 
appeared  quite  satisfactory  when  projected  in  small  review  rooms  with  a  screen 
illumination  several  times  as  great  as  that  obtainable  in  the  theater.  Chairman 
H.  Rubin  announced  that  definite  action  is  being  taken  by  producers  in  adopting 
the  recommendations  of  the  Committee  for  improving  the  visibility  of  change-over 
marks  on  films,  the  recommended  marks  taking  the  form  of  black  spots  surrounded 
by  clear  circles  so  that  they  can  be  easily  distinguished  by  the  projectionist 
against  either  a  light  or  dark  background.  The  work  of  collecting  data  on  the 
clearances,  tolerances,  and  tensions  of  projectors,  begun  some  time  ago,  is  pro- 
gressing, and  the  Committee  hopes  to  have  the  material  sufficiently  complete  for 
presentation  to  the  Society  within  several  months.  A  new  test  reel  is  being  de- 
veloped by  the  Committee  for  the  use  of  exhibitors  in  testing  the  adjustments  of 
their  projection  equipment.  The  mere  running  of  this  test  film  in  the  theater  will 
provide  visual  and  aural  means  of  detecting  misadjustments  of  the  optical  system 
of  the  projector,  etc.,  and  will  also  indicate  what  adjustments  are  necessary  for  the 
correction  of  travel  ghost,  chromatic  aberration,  sound  track  adjustments,  and 
the  like.  The  test  film  will  be  presented  to  the  Society  at  the  Spring  Convention, 
April  24  to  28,  at  New  York,  N.  Y. 


Bausch  &  Lomb  Optical  Co. 
Bell  Telephone  Laboratories 
Burnett-Timken  Laboratories 

Eastman  Kodak  Co. 

Electrical  Research  Products,  Inc. 

National  Carbon  Co. 

RCA  Victor  Co.,  Inc. 




By  action  of  the  Board  of  Governors,  October  4,  1931,  this  Honor  Roll  was  estab- 
lished for  the  purpose  of  perpetuating  the  names  of  distinguished  pioneers  who  are 
now  deceased: 




Type    3S   Com-  Single  or  Double  System,  Variable 

plete      Record-  Density  or  Variable  Area,  Studio 

or  Portable. 

Write  or  cable  for  literature 


3333  Belmont  Ave. 
Chicago,  U.  S.  A. 

Cable  Address:    JENKADAIR 


Since  the  entire  audio-frequency  range 
is  covered  by  rotating  a  single  dial,  the 
beat-frequency  oscillator  is  extremely 
useful  for  rapid  studies  of  audio-fre- 
quency equipment.  The  General  Radio 
Company  manufactures  two  models  of 
beat-frequency  oscillators,  one  for  alter- 
nating-current operation  and  the  other 
operated  from  batteries. 

TYPE  513-B  (alternating-current  operated)  ....  $450.00 
TYPE  613-A  (battery-operated) 210.00 




Manufacturers  of  motion  picture  equipment  and  supplies  are  requested  to  send 
to  the  General  Office  of  the  Society  copies  of  their  descriptive  pamphlets,  book- 
lets, and  catalogues  as  issued.  Notices  of  the  issuance  of  this  material  will  be 
published  in  the  JOURNAL,  advising  the  readers  that  the  material  may  be  obtained 
free  of  charge  by  addressing  the  manufacturers  named.  This  editorial  service 
has  been  established  in  order  to  acquaint  readers  of  the  JOURNAL  with  the  com- 
mercial developments  of  the  motion  picture  industry  as  quickly  as  they  occur. 




Volume  XX                          MARCH,  1933                          Number  3 


Report  of  the  Committee  on  the  Care  and  Development  of 
Sub-Committee  on  Laboratory  Practice  






Sub  -Commit  tee  on  Exchange  Practice  

Film  Recorders  A.  G.  ZIMMERMAN 

The  Relation  between  Diffuse  and  Specular  Density  

Model  Making  with  Sheet  Film  Base  


The  Depicting  of  Motion  Prior  to  the  Advent  of  the  Screen.  .  . 

The  History  of  Nitrocellulose  as  a  Film  Base  E.  THEISEN 
Early  Stages  of  Kinematography       C.  H.  BOTHAMLEY 

Book  Review  



Society  Announcements  

Catalogues  Received   





Board  of  Editors 

J.  I.  CRABTREE,  Chairman 



Published  monthly  at  Easton,  Pa.,  by  the  Society  of  Motion  Picture  Engineers. 

Publication  Office,  20th  &  Northampton  Sts.,  Easton,  Pa. 
General  and  Editorial  Office,  33  West  42nd  St.,  New  York,  N.  Y. 

Copyrighted,  1933,  by  the  Society  of  Motion  Picture  Engineers,  Inc. 

Subscription  to  non-members,  $12.00  per  annum;  to  members,  $9.00  per  annum, 
included  in  their  annual  membership  dues;  single  copies,  $1.50.  A  discount 
on  subscriptions  or  single  copies  of  15  per  cent  is  allowed  to  accredited  agencies. 
Order  from  the  Society  of  Motion  Picture  Engineers,  Inc.,  20th  and  Northampton 
Sts..  Easton,  Pa.,  or  33  W.  42nd  St.,  New  York,  N.  Y. 

Papers  appearing  in  this  Journal  may  be  reprinted,  abstracted,  or  abridged 
provided  credit  is  given  to  the  Journal  of  the  Society  of  Motion  Picture  Engineers 
and  to  the  author,  or  authors,  of  the  papers  in  question. 

The  Society  is  not  responsible  for  statements  made  by  authors. 

Entered  as  second  class  matter  January  15,  1930,  at  the  Post  Office  at  Easton, 
Pa.,  under  the  Act  of  March  3,  1879. 



The  following  report,  reviewing  the  conditions  as  actually  found  at  present  in  the 
field,  is  intended  as  an  introduction  to  a  more  detailed  and  technical  study  of  laboratory 
practice,  to  be  reported  on  later.  All  the  phases  of  handling  and  treating  both  un- 
exposed  and  exposed  film  in  laboratories  are  discussed,  beginning  with  the  testing 
of  the  raw  stock  as  received  by  the  laboratory,  passing  through  the  exposing,  develop- 
ing, fixing,  washing,  and  drying  of  the  film  and  concluding  with  duplicating  and 
several  subsidiary  operations.  Following  the  initial  work  of  the  sub-committee 
represented  by  the  studies  of  existing  conditions  described  in  this  report,  the  sub- 
committee purposes  in  the  future  to  report  separately  on  each  of  the  above  phases. 


A.  Testing 

B.  Exposing 

C.  Developing 

D.  Fixing 

E.  Washing 

F.  Drying 

G.  Conditioning 
H.  Cutting 

/.       Printing 
/.       Duplicating 
K.      Seasoning 


Testing.  When  producers  of  motion  pictures  began  to  record  sound  on  film 
in  addition  to  the  scenes,  the  problems  of  processing  became  more  involved. 
Factors  that  had  been  allowed  to  vary  with  impunity  had  to  be  maintained 
constant,  and  sensitometric  equipment,  requiring  for  its  operation  trained  men, 
had  to  be  installed.  New  emulsions  were  prepared  in  the  attempt  to  obtain  a 
higher  quality  of  picture  and  sound  records. 

Exposing.  The  theory  of  sensitometry  is  quite  explicit  in  defining  the  proper 
exposure  of  the  negative.  However,  no  standard  rules  of  exposure  can  be  strictly 
adhered  to  in  producing  motion  pictures  owing  to  the  numerous  variations  in 
working  conditions  and  the  many  special  effects  desired.  The  greatest  degree 
of  coordination  is  required  between  the  cameramen  and  the  laboratory  technicians 
if  the  best  quality  pictures  are  to  be  obtained. 


184  CARE  AND  DEVELOPMENT  OF  FILM         [j.  s.  M.  P.  E. 

Developing.  In  order  to  increase  the  quantity  of  film  processed  and  improve 
the  quality  of  the  product,  machines  are  now  used  in  all  large  laboratories  for 
developing  film.  Three  methods  of  controlling  the  process,  or  various  combina- 
tions of  these  three  methods,  are  usually  employed:  (1)  sampling,  (2)  time  and 
temperature,  and  (3)  sensitometric.  Each  of  these  methods  has  its  own  advantages. 

Fixing.  Alum  fixing  baths  are  most  commonly  used,  as  they  require  very 
little  attention.  The  motion  of  the  film  through  the  bath  usually  causes  sufficient 
agitation  of  the  solution  to  assure  sufficiently  complete  fixing. 

Washing.  In  most  instances  the  tap  water  runs  directly  through  the  washing 
tanks  to  the  drain.  In  some  few  locations  it  may  be  necessary  to  cool  the  water 
during  the  warm  season. 

Drying.  Conditioned  air  of  the  proper  temperature  and  humidity  is  circulated 
through  the  drying  cabinets.  The  curl  of  the  film  usually  provides  an  index  of 
the  proper  conduct  of  the  drying  procedure. 

Conditioning.  To  prevent  the  accumulating  of  dust  and  dirt  on  the  film,  only 
conditioned  air  is  admitted  into  the  developing,  printing,  and  assembling  rooms. 
The  improvement  in  the  quality  of  the  film,  due  to  guarding  it  against  dirt  and 
scratches,  has  more  than  offset  the  cost  of  the  conditioning  equipment. 

Cutting.  The  introduction  of  the  sound  negative  demanded  a  new  technic 
in  cutting  and  assembling.  The  addition  of  music  and  other  kinds  of  sounds 
requires  thorough  technical  training  of  the  cutter. 

Printing.  Several  types  of  mechanical  devices  are  now  used  to  determine  the 
proper  printing  exposure.  The  uniformity  of  development  that  occurs  in  de- 
veloping machines  is  an  important  factor  that  assists  in  properly  determining  the 
exposure  of  the  negatives.  Trained  technicians  maintain  the  exposure  scales  of 
the  printers  constant  and  uniform. 

Duplicating.  Special  emulsions  and  printers  are  used  in  attempting  to  match 
the  quality  of  the  duplicate  print  and  that  of  the  original  print.  The  contrast 
can  be  matched  by  appropriately  developing  the  film,  although  graininess  may 
increase  and  loss  of  definition  occur. 

Seasoning.  Many  patented  methods  are  in  vogue  to  protect  the  film  and 
lengthen  its  useful  life.  The  most  common  method  of  seasoning  consists  in 
applying  about  the  perforations  a  small  quantity  of  wax,  which  decreases  the 
friction  and  the  tendency  to  tear  during  the  process  of  projecting  the  picture. 

It  is  here  purposed  merely  to  describe  briefly  the  methods  generally 
employed  by  the  industry  in  the  development  and  care  of  film.  Thus, 
the  committee  submits  this  report  to  the  Society  with  the  desire 
that  it  be  considered  as  an  introduction  to  the  reports  to  follow,  in 
which  the  respective  operations  in  this  field  will  be  studied  indi- 
vidually, both  from  the  standpoint  of  actual  practice  and  from  the 
existing  literature. 

At  the  completion  of  such  a  survey  of  each  operation  of  the  pro- 
ducers in  converting  an  emulsion  into  a  finished  print,  and  dis- 
tributing the  print  to  the  exhibitors,  the  Committee  will  be  in  a 

Mar.,  1933]  LABORATORY  PRACTICE  185 

position  to  attempt  to  make  recommendations  for  the  standardiza- 
tion of  laboratory  and  exchange  practice. 

On  examining  the  bibliography  in  this  field,  it  was  found  to  be 
extremely  lengthy.  Thus,  rather  than  attempt  to  present  a  general 
bibliography  in  this  report,  it  has  appeared  advisable  to  subdivide 
and  list  the  literature  in  later  reports  with  the  respective  operation  to 
which  it  pertains. 

In  this  general  discussion,  it  may  frequently  appear  that  the  report 
includes  subjects  outside  the  purview  of  this  sub-committee.  How- 
ever, it  was  concluded  that  any  factor  such  as  the  characteristic  of 
the  emulsion  or  the  nature  of  the  exposure  that  might  affect  the 
quality  of  the  finished  print  should  be  considered.  The  quality  of 
the  laboratory  work  is  judged  by  the  release  print. 


The  proper  processing  of  sound  film,  when  introduced  into  the 
laboratories,  necessitated  an  increase  of  personnel.  The  requirements 
of  the  sound  engineers  could  be  correctly  interpreted  and  properly 
fulfilled  only  by  those  familiar  with  the  theory  of  sensitometry. 
Some  laboratories  realized  this  fact,  and  either  engaged  additional 
help  or  properly  trained  some  of  their  own  employees.  Various 
types  of  sensitometers  were  installed,  and  sensitometric  practice 
soon  became  a  part  of  laboratory  practice.  The  film  manufacturing 
companies  were  particularly  helpful  in  supplying  and  calibrating 
equipment  and  in  training  the  personnel. 

After  the  practice  of  continually  checking  and  maintaining  de- 
velopers and  printers  had  been  instituted,  it  became  apparent 
that  frequently  variations  were  introduced  by  new  emulsions. 
Checking  new  emulsions  for  speed  and  contrast  then  became  an  addi- 
tional function  of  the  new  department. 

Various  types  of  equipment  were  tried,  with  more  or  less  moderate 
success.  Photocell  densitometers  were  developed  for  the  rapid 
reading  of  sound  track  densities.  In  most  instances,  operators  have 
returned  to  such  standard  equipment  as  a  calibrated  wedge  or  Nicol 
prism  densitometers.  Densities  are  usually  read  with  the  emulsion 
facing  a  diffused  light.  Sensitometric  exposures  are  usually  made  in 
variable  time  steps  with  a  high-intensity  light.  Unless  otherwise 
stated,  all  reference  made  in  this  report  to  densities  and  contrast  will 
imply  this  type  of  measurement. 

Practically  all  motion  pictures  now  made  in  this  country  are  made 

186  CARE  AND  DEVELOPMENT  OF  FILM        [j.  S.  M.  p.  E. 

on  panchromatic  negative  stock.  The  process  of  making  film  pan- 
chromatic consists  essentially  of  adding  dyes  to  the  emulsion  to  ob- 
tain the  desired  spectral  response. 

With  the  advent  of  sound  pictures,  it  became  necessary  for  some 
producers  to  replace  the  noisy  carbon  lights  with  silent  incandescent 
lamps.  The  incandescent  lamps,  the  energy  radiation  of  which  was 
much  greater  at  the  longer  wavelengths,  permitted  the  emulsion 
makers  to  increase  appreciably  the  speed  of  their  product  by  in- 
creasing the  sensitivity  of  the  emulsion  to  the  red  end  of  the  spectrum. 
This  change  permitted  a  decrease  of  the  required  lighting  and,  in 
general,  resulted  in  an  improvement  in  quality  of  the  pictures  owing 
to  the  closer  equivalence  of  the  spectral  response  of  the  film  to  that 
of  the  eye.  However,  these  advantages  are  not  so  important  on 
exterior  pictures  where  many  producers  continue  to  use  regular 
panchromatic  stock. 

The  addition  of  a  gray  coating  to  the  film  base  resulted  in  the  ab- 
sorption, by  the  base,  of  the  light  transmitted  through  the  emulsion, 
thus  preventing  the  reflection  of  light  back  into  the  emulsion  and 
additional  exposure  caused  thereby.  Approximately  sixty  per  cent 
of  the  negative  emulsions  now  used  employ  the  non-halation  gray 
base.  Emulsion  makers  are  continually  improving  their  product 
by  increasing  the  speed,  decreasing  the  grain,  and  adding  to  the 
general  quality  of  the  finished  print. 

Due  to  its  low  cost  and  uniform  characteristics,  positive  film  is 
always  used  for  recording  sound  on  a  film  separate  from  that  contain- 
ing the  picture.  Most  productions  are  made  by  this  double  system 
in  order  to  permit  the  selection  of  a  proper  emulsion  and  negative 
developer  for  the  sound  recording.  Numerous  new  emulsions  have 
been  made  in  attempts  to  improve  the  volume  and  quality  of  the 
sound  records.  Emulsions  of  high  gamma  infinity  have  been  made 
for  variable  width  records,  and  emulsions  with  a  low  gamma  infinity 
have  been  made  for  variable  density  records.  High-speed  positive 
emulsions  have  been  made  for  flashing  lamp  recording  to  permit  the 
use  of  a  lower  intensity  of  unmodulated  light,  thus  demanding  a 
smaller  polarizing  current  and  tending  to  increase  the  life  of  the 

In  single  system  records,  where  sound  and  picture  are  recorded  on 
the  same  film,  the  sound  can  not  be  given  much  consideration. 
Both  the  negative  emulsion  characteristics  and  the  negative  develop- 
ment must  be  confined  to  those  limits  that  are  satisfactory  for  the 

Mar.,  1933]  LABORATORY  PRACTICE  187 

picture.  The  single  system  of  recording  is  used  only  when  portability 
of  equipment  is  more  important  than  high  quality  of  sound.  Its 
chief  use  is  found  in  news  photography,  in  which  the  necessary  equip- 
ment is  materially  decreased  by  having  to  employ  only  a  single 

Emulsions  for  printing  are  low  in  price,  high  in  contrast,  mono- 
chromatic in  response,  slow  of  speed,  and  of  extremely  fine  grain 
Several  hundred  prints  are  frequently  made  from  a  single  negative. 
This  permits  the  manufacturers  to  produce  positive  film  more  eco- 
nomically on  large-scale  production.  Film  manufacturing  losses 
increase  with  the  speed  of  an  emulsion.  Dye  sensitization  is  unneces- 
sary with  monochromatic  emulsions.  It  is  therefore  possible  to 
obtain  positive  emulsions  for  a  fraction  of  the  cost  of  negative  emul- 

The  positive  film  must  be  high  in  contrast  to  permit  the  required 
over-all  gamma  of  unity  to  be  obtained  without  excessive  negative 
development.  As  the  high  speed  of  the  negative  entails  a  coarse 
grain,  the  development  is  limited  to  low  values  of  gamma  at  which  the 
grain  is  not  objectionable. 

Lamps  of  almost  any  type  or  intensity  can  be  used  in  the  printing 
machines.  Therefore,  economy  of  manufacture  chiefly  governs  the 
speed  and  spectral  response  of  the  positive  film.  The  low  speed 
permissible  with  positive  emulsions  permits  us  to  realize  the  ad- 
vantages of  fine  grain  structure. 


According  to  photographic  theory,  the  visual  tone  scale  of  a  scene 
can  be  matched  on  a  print  only  when  the  negative  and  print  are 
properly  exposed.  The  region  of  correct  exposure  of  a  particular 
emulsion  can  be  determined  by  plotting  the  characteristic  from  the 
density  readings  of  a  sensitometric  strip  of  the  emulsion.  If  the 
density  be  plotted  against  the  logarithm  of  the  exposure,  the  region 
of  correct  exposure  will  be  a  straight  line.  On  a  negative  picture, 
developed  with  a  sensitometric  strip,  those  portions  of  the  scene  that 
produce  densities  that  fall  along  the  straight  line  are  properly  ex- 
posed. Theoretically  all  other  portions  are  either  overexposed  or 
underexposed.  This  is  true  also  of  the  print. 

In  practice,  the  improper  exposure  of  a  negative  is  easily  detected 
by  inspection.  If  details  be  lacking  in  the  shadows,  the  film  is  under- 
exposed; or,  if  it  be  lacking  in  the  highlights,  the  film  is  overexposed. 

188  CARE  AND  DEVELOPMENT  OF  FILM        [j.  S.  M.  p.  E. 

Since  it  is  extremely  difficult  to  reproduce  faithfully  the  complete 
range  of  tones  visible  in  the  usual  scene,  the  exposure  is  adjusted 
for  the  objects  of  principal  importance.  As  the  time  of  exposure 
of  all  sound  pictures  must  be  constant,  the  exposing  light  must  be 
adjusted  so  as  to  obtain  the  proper  exposure.  Trained  cameramen 
seldom  fail  to  expose  their  film  properly  when  they  are  working  under 
normal  conditions.  It  is  much  more  difficult,  however,  to  achieve 
the  proper  lighting  contrast.  Often  a  cameraman  returns  to  a  set 
for  the  purpose  of  photographing  additional  scenes  or  making  re- 
takes after  a  lapse  of  several  weeks.  He  must  attempt  to  duplicate 
his  previous  lighting  so  that  his  new  negatives  will  properly  match  the 
previously  exposed  negatives,  both  in  density  and  contrast.  A 
change  of  light  intensity  in  printing  can  often  compensate  for  a  change 
of  negative  density,  but  a  change  of  contrast  can  be  corrected  only  by 
varying  the  negative  development. 

The  usual  procedure  followed  in  photographing  a  scene  is  for  the 
director  to  describe  to  the  cameraman  the  lighting  effects  desired  on 
the  screen  when  the  print  is  projected.  The  cameraman  attempts  to 
accomplish  what  the  director  desires  by  adjusting  the  positions  of  his 
light  sources,  the  intensity  of  the  light,  the  color  of  the  light,  and  the 
amount  of  diffusion.  These  adjustments  are  based  on  his  experience 
with  numerous  scenes  photographed  under  various  lighting  conditions, 
which  he  had  subsequently  viewed  on  the  screen.  The  cameraman 
must  be  very  familiar  with  the  characteristics  of  both  the  negative 
emulsion  and  the  manner  of  developing  in  the  laboratory.  If  he 
makes  an  error  in  judging  the  lighting  of  the  set,  the  laboratory  may  or 
may  not  be  able  to  help  him,  depending  upon  the  type  of  negative 
development  control  employed. 

There  are  three  principal  methods  of  exposing  sound  negatives.  In 
the  variable  width  system,  a  mirror  attached  to  a  vibrating  gal- 
vanometer unit  reflects  a  beam  of  light  upon  the  moving  film,  pro- 
ducing a  sound  track  of  varying  width.  There  are  two  methods  of 
exposing  variable  density  sound  tracks.  In  one  case,  a  light  beam  of 
constant  intensity  impinges  upon  the  moving  film  through  a  slit, 
the  variation  of  whose  width  changes  the  time  of  exposure.  In  the 
second,  the  film  is  exposed  to  a  modulated  light  beam  through  a 
slit  of  fixed  width  and  the  intensity  of  the  exposing  light  is  varied. 

In  variable  density  recording,  the  same  rules  concerning  exposure 
apply  as  in  exposing  a  negative  picture.  Overexposure  or  under- 
exposure of  the  sound  track  causes  audible  distortion  just  as  similar 

Mar.,  1933]  LABORATORY  PRACTICE  189 

errors  made  in  exposing  the  picture  negative  cause  visible  distortion. 
Improper  exposure  in  variable  width  recording  does  not  usually  re- 
sult in  distortion,  but  causes  a  change  of  volume. 

In  photographing  a  scene  by  the  double  system,  a  strict  routine  is 
followed  to  insure  the  proper  marking  of  the  film  and  thus  enable  the 
laboratory  to  print  the  sound  and  picture  negatives  in  synchronism. 
At  a  signal  from  the  director,  the  sound  machine  and  camera  are 
started  on  an  interlocked  system.  The  sound  man  or  his  assistant 
indicates  when  his  machine  has  reached  synchronous  speed.  The 
assistant  cameraman  announces  the  feature,  scene,  and  "take" 
numbers  before  the  microphone.  Action  follows  until  the  cameras 
are  stopped  at  a  signal  from  the  director.  With  the  cameras  and 
sound  machine  still  interlocked,  the  cameraman  and  sound  man 
make  synchronizing  marks  on  their  respective  films.  The  sound  man 
also  punches  the  feature,  scene,  and  take  numbers  on  his  film.  The 
cameraman  photographs  a  slate  bearing  the  same  information.  The 
films  are  now  completely  equipped  with  identifying  marks. 

The  routine  of  different  companies  varies  somewhat  in  obtaining 
the  same  results.  Some  companies,  in  preference  to  making  syn- 
chronizing marks,  photograph  the  action  and  record  the  sound  of 
some  simple  device,  such  as  that  made  by  two  pieces  of  wood  struck  to- 
gether. The  cutter  soon  learns  to  recognize  the  sound  record  of  this 
signal  noise  as  a  synchronizing  mark  on  the  sound  track. 


All  developing  done  by  the  major  laboratories  is  now  accomplished 
in  machines  in  which  the  film  is  mechanically  moved  through  the 
developer  at  constant  speed.  The  exposed  film  is  fed  to  the  machine 
at  one  end;  and  the  developed,  fixed,  and  dried  film  is  emitted  at 
the  other  end.  Since  many  of  the  laboratories  designed  their  own 
machines  to  suit  their  specific  requirements,  numerous  types  are 
found  in  operation.  They  may  be  roughly  divided  into  two  classes: 
those  in  which  the  film  moves  perpendicularly,  and  those  in  which  it 
moves  horizontally. 

The  developer  is  continuously  circulated  through  a  cooling  system. 
In  some  machines  thermostats  automatically  maintain  the  tem- 
perature constant  within  one  degree.  The  temperature  of  operation 
varies  at  different  laboratories  from  65°F.  to  68°F.  The  developer  is 
maintained  at  a  given  strength  by  automatically  introducing  addi- 
tional developer  into  the  circulating  system. 

190  CARE  AND  DEVELOPMENT  OF  FILM         [J.  S.  M.  P.  E. 

Considerable  variation  can  be  found  in  the  speed  at  which  the 
film  travels  through  the  developer  in  different  developing  machines. 
While  the  average  speed  for  negative  film  is  about  sixty  feet  per 
minute,  speeds  as  low  as  twenty  feet  per  minute  and  as  high  as  one 
hundred  feet  per  minute  can  be  found  at  various  laboratories. 

Similarly,  the  time  of  development  of  negatives  varies  from  eight 
to  twenty  minutes,  depending  upon  the  agitation,  rate  of  circulation, 
and  strength  of  the  developer.  Negative  developing  gammas  vary 
from  0.50  to  0.65. 

Although  the  negative  developers  used  in  different  laboratories 
vary  in  concentration,  their  basic  constituents  are  usually  identical: 
monomethyl-para-aminophenol  sulfate,  hydroquinone,  borax,  and 
sodium  carbonate.  The  concentration  of  these  ingredients  is  varied 
to  permit  the  most  efficient  operation  of  the  different  machines. 
When,  due  to  lack  of  space,  a  laboratory  is  obliged  to  use  a  small 
machine,  it  is  necessary  to  use  a  fast  working  developer  in  order  to 
obtain  the  proper  contrast,  unless  the  laboratory  is  willing  to  operate 
at  lower  efficiency  and  operate  the  machines  more  slowly. 

Three  types  of  control  of  negative  development  are  in  use.  In  the 
time-and-temperature  system,  all  negatives,  regardless  of  exposure, 
are  developed  for  a  fixed  length  of  time.  The  bath  is  supposedly 
maintained  at  a  constant  strength  and  constant  temperature.  The 
strength  of  the  bath  is  checked  at  regular  intervals  by  means  of  what 
is  supposed  to  be  a  standard  exposed  negative. 

In  the  sampling  system,  the  cameraman  submits  a  sample  negative 
of  every  new  scene,  which  is  developed  for  a  standard  length  of  time. 
By  inspection  of  the  developed  sample,  the  proper  time  of  develop- 
ment of  the  particular  scene  is  determined.  This  method  places 
considerable  responsibility  on  the  inspector,  who  must  always  be  in 
close  contact  with  the  cameraman  in  order  to  know  the  type  of  picture 

Sensitometric  control  is  used  as  a  third  method  of  controlling  the 
development  of  negatives.  Sensitometric  strips  are  inserted  at  fre- 
quent intervals  to  determine  precisely  the  contrast  of  development 
and  the  density  obtained  from  a  given  exposure.  These  factors  are 
maintained  constant  by  varying  the  time  of  development  or  by  in- 
creasing the  rate  of  flow  of  additional  or  fresh  developer  into  the 
circulating  system.  The  usual  practice,  followed  when  the  con- 
trast or  density  is  found  to  have  changed  appreciably,  is  to  vary, 
first,  the  time  of  development.  This  correction,  which  causes  im- 

Mar.,  1933]  LABORATORY  PRACTICE  191 

mediate  results,  can  be  realized  either  by  varying  the  speed  of  the  ma- 
chine or  by  changing  the  length  of  the  film  in  the  developer.  This 
second  method  of  making  the  correction  consists  in  varying  either 
the  lengths  of  the  loops  of  film  in  the  developer,  or  in  changing  the 
number  of  loops.  The  rate  of  flow  of  additional  or  fresh  developer 
is  then  adjusted  so  that  the  developer  soon  returns  to  its  normal 
strength.  The  machine  is  then  readjusted  for  normal  operation. 

Due  to  the  numerous  adverse  conditions  that  a  cameraman  must 
continually  face,  it  is  necessary  that  the  laboratory  assist  as  much  as 
possible  toward  obtaining  a  good  negative.  While  it  is  not  very 
desirable,  in  order  to  obtain  perfect  negatives,  to  have  to  compensate 
for  excessive  or  insufficient  exposure,  it  is  possible  and  often  practi- 
cable to  compensate  for  excessive  or  insufficient  contrast.  Thus, 
in  a  laboratory  in  which  the  sampling  method  is  used,  it  is  frequently 
possible  to  match  approximately  negatives  that  have  been  exposed 
under  different  lighting  conditions.  For  very  flat  lighting,  the  de- 
velopment is  increased;  and  for  very  contrasty  lighting,  the  develop- 
ment is  decreased.  Of  course,  the  negative  development  must  not 
be  increased  to  such  an  extent  as  to  permit  the  negative  grain  to  be- 
come objectionable.  Extreme  care  must  be  taken  at  the  laboratory  to 
interpret  correctly  the  lighting  effects  desired  by  the  cameraman  and 
director.  The  cameraman  should  always  be  advised  of  any  variation 
made  in  his  favor  to  aid  him  in  future  lighting. 

Although  positive  emulsions  are  used  for  variable  density  sound 
negatives,  they  are  usually  developed  in  a  negative  bath.  This  is  a 
low  gamma  bath,  which  permits  a  reasonable  developing  time  for 
the  desired  low  contrasts  of  0.40  to  0.55.  An  exception  to  this  occurs 
when  developing  negatives  recorded  by  the  flashing  lamp,  in  which 
case  the  records  are  frequently  developed  with  the  regular  prints  to  a 
gamma  of  2.0  to  2.2.  This  high  negative  development  tends  to 
correct  the  distortion  due  to  the  underexposure.  The  volume  level 
of  the  signal  on  the  print  also  increases  with  the  negative  develop- 

In  variable  width  records  it  is  highly  desirable  to  develop  the 
negative  to  the  full  extent  if  the  maximum  volume  is  to  be  obtained. 
Frequently  a  special  high  gamma  developer  is  employed,  and  gammas 
as  high  as  3.0  are  found. 

The  usual  bath  employed  in  developing  prints  is  of  the  type  em- 
ploying monomethyl-para-aminophenol  sulfate  and  hydroquinone. 
The  desired  contrast  of  development  varies  from  1.80  to  2.20.  The 

192  CARE  AND  DEVELOPMENT  OF  FILM         [j.  S.  M.  P.  E. 

permissible  variation  during  operation  is  approximately  five  per  cent. 
It  is  extremely  important  that  the  density  obtained  in  the  positive 
bath  after  a  given  exposure  remain  constant.  Frequently  orders 
come  to  the  laboratory  for  reprints  of  negatives  that  have  been  timed 
several  weeks,  or  even  months,  previously.  If  originally  the  bath 
had  been  properly  maintained  and  if  the  new  bath  is  made  to  match 
the  original  bath  properly,  it  becomes  possible  to  use  the  old  printing 
cards  that  indicate  the  proper  printing  step  for  each  negative  scene. 
If,  on  the  other  hand,  the  strength  of  the  original  bath  had  been  al- 
lowed to  vary,  the  negatives  made  in  later  baths  would  require  retiming 
for  all  reprints  and  the  timer  would  never  be  certain  of  his  results. 

Sensitometric  exposures  are  usually  employed  to  check  the  con- 
trast and  density  obtained  in  the  positive  bath.  However,  a  print 
made  from  a  standard  negative  and  a  standard  printer  is  also  used  as 
an  additional  visual  check. 

Positive  developing  machines  are  usually  constructed  to  run  at 
higher  speeds  than  negative  developing  machines.  The  printed  film 
is  not  as  valuable  as  the  negative,  and  in  case  of  damage  it  can  easily 
be  replaced.  Due  to  the  brevity  of  time  between  completing  the 
photographing  of  a  picture  and  releasing  it,  it  is  usually  necessary  to 
operate  the  positive  machines  at  high  speeds  in  order  to  adhere  to  the 
laboratory's  schedule. 

The  average  speed  of  the  positive  machines  is  about  110  feet  per 
minute.  Some  laboratories  develop  as  much  as  150  feet  of  film  per 
minute,  while  others  develop  as  little  as  80  feet  per  minute.  The  tem- 
perature of  the  bath  is  maintained  constant  within  a  degree.  The 
average  operating  temperature  is  about  66°F.  The  time  of  develop- 
ment varies  from  three  and  a  half  to  eight  minutes,  depending  upon 



Most  laboratories  use  an  acid  or  a  chrome  alum  fixing  bath. 
An  acid  bath  must  be  watched  so  as  to  guard  against  precipitation, 
which  may  cause  an  undesirable  deposit  on  the  film.  In  general 
practice,  the  fixing  solution  is  neither  mechanically  circulated  nor 
thermostatically  controlled.  The  temperature  of  the  room  and  the 
proximity  of  the  washing  tanks  are  sufficient  to  maintain  the  tem- 
perature below  68° F.  When  the  temperature  is  allowed  to  exceed 
70 °F.,  the  grain  of  the  film  increases  and  sulfur  dioxide  may  be 
released.  The  motion  of  the  film  through  the  solution  causes  suf- 
ficient agitation  for  proper  fixing. 

Mar.,  1933]  LABORATORY  PRACTICE  193 

The  strength  of  the  fixing  bath  is  checked  by  noting  the  point  in 
the  machine  at  which  the  film  becomes  clear.  When  this  point 
approaches  the  vicinity  of  the  wash  tanks,  the  solution  is  strengthened 
by  replacing  some  of  it  with  fresh  solution. 

The  average  time  of  fixing  negative  film  varies  from  8  to  12  minutes. 
Several  minutes  less  are  sufficient  for  fixing  positives. 


Wash  water  is  usually  obtained  directly  from  the  main  supply. 
In  some  instances  during  warm  seasons,  some  rough  method  of 
cooling  may  be  required.  Normally,  however,  the  temperature  of  the 
tap  water  does  not  exceed  70 °F.,  which  is  satisfactory  for  washing. 
The  water  flows  continuously  from  the  main  into  the  wash  tanks, 
and  thence  to  the  drain. 

A  chemical  test  is  frequently  employed  to  determine  whether  the 
film  has  been  sufficiently  washed.  The  drippings  from  the  film 
can  easily  be  tested  for  the  presence  of  hypo  by  adding  a  solution  of 
potassium  carbonate  and  potassium  permanganate  in  water.  A 
greenish  yellow  color  results  when  hypo  is  present.  The  average 
time  of  washing  negative  film  varies  from  10  to  15  minutes.  Several 
minutes  less  of  washing  are  sufficient  for  positive  film. 

F.     DRYING 

Since  the  universal  adoption  of  machine  methods  of  developing 
film,  the  drum  method  of  drying  is  no  longer  used.  By  the  modern 
methods,  film  is  dried  in  cabinets  through  which  conditioned  air 
circulates.  The  relative  humidity  of  the  air  is  maintained  at  ap- 
proximately 40  per  cent,  at  a  temperature  of  about  73 °F.  In  some 
instances,  when  the  machines  are  required  to  operate  at  maximum 
capacity,  temperatures  as  high  as  110°F.  are  necessary  in  order  to  be 
sure  that  the  film  becomes  sufficiently  dry.  However,  it  is  con- 
sidered poor  practice  to  operate  under  such  conditions,  85°F.  being 
supposedly  the  optimal  temperature  for  drying. 

The  rate  of  flow  of  air  required  for  complete  drying  depends  upon 
the  construction  of  the  cabinets,  the  position  of  the  baffles,  and  other 
variables.  An  operator  constantly  checks  the  drying  of  the  film 
by  inspecting  the  curl  of  the  film  through  the  glass  doors  of  the  drying 


Laboratories  have  found  it  necessary  during  the  last  few  years 
to  be  equipped  with  high-grade  air  conditioning  systems.  All  dust 

194  CARE  AND  DEVELOPMENT  OF  FILM         [j.  s.  M.  p.  E. 

particles  must  be  removed  from  the  air  admitted  to  the  developing, 
printing,  and  assembling  rooms,  and  particularly  from  the  air  forced 
through  the  drying  cabinets.  The  temperature  and  humidity  of  the 
air  in  the  drying  cabinets  are  also  maintained  constant.  Automatic 
temperature  and  humidity  controls  are  installed  in  order  to  maintain 
the  proper  drying  conditions  regardless  of  the  exterior  atmospheric 
conditions.  The  temperature  and  humidity  of  the  air  in  some  of  the 
laboratory  workrooms  are  also  controlled ;  particularly  in  the  printing 
room,  where  a  relative  humidity  of  65  to  70  per  cent,  at  a  temperature 
of  approximately  70 °F.,  is  maintained  in  order  to  prevent  the  static 
discharges  that  sometimes  occur  when  exposing  raw  emulsions. 

The  cycle  of  air  conditioning  is  roughly  as  follows :  Air  is  admitted 
through  a  vent  into  a  heating  chamber.  After  a  suitable  adjustment 
of  the  temperature,  it  is  mixed  with  the  air  that  is  being  recirculated. 
It  is  then  forced  through  an  automatic  filter  into  the  water  spray 
chamber,  where  the  air  is  washed  and  given  the  proper  temperature 
and  humidity.  The  air  is  drawn  from  this  chamber,  forced  into  the 
ducts,  and  distributed.  In  addition  to  this  air  conditioning  unit, 
a  heating  system  and  a  refrigerating  unit  are  also  required. 


After  being  properly  dried,  the  sound  and  picture  negatives  are 
cut  into  single  takes  and  properly  marked  for  printing.  The  marks 
are  so  made  as  to  compensate  for  the  approximate  15- inch  displace- 
ment required  by  the  projector  for  synchronized  reproduction. 

A  complete  list  of  all  takes  is  submitted  to  the  laboratory  by  the 
cameraman.  This  list  aids  the  cutter  in  assembling  and  marking 
the  film,  and  furnishes  advice  to  the  laboratory  as  to  which  negatives 
are  to  be  printed.  Numerous  takes  are  spoiled,  due  to  improper 
action,  which  are  not  printed.  Rush  prints  of  all  desirable  takes  are 
usually  made  immediately  following  the  negative  development  to 
permit  screening  by  the  director  on  the  day  following  the  photograph- 
ing. After  screening,  the  rush  prints  are  handed  to  the  positive 
cutter,  who  cuts,  assembles,  and  selects  the  scenes  as  advised  by 
the  director.  After  all  the  scenes  have  been  photographed  and  the 
rush  prints  have  been  cut  and  assembled  into  a  complete  print  satis- 
factory tp  the  director,  the  print  is  handed  to  the  negative  cutters, 
who  cut  and  assemble  the  sound  negative  to  match  the  rush  print. 
A  complete  new  sample  print  is  then  made,  which  is  cut  and  re- 
assembled until  the  director  and  producers  are  completely  satisfied. 

Mar.,  1933]  LABORATORY  PRACTICE  195 

The  negative  is  again  cut  to  match  the  corrected  print,  and  a  second 
sample  print  is  produced.  Titles,  fades,  musical  accompaniment, 
and  extraneous  sounds  are  all  added  before  the  second  sample  is 
printed.  If  the  second  sample  is  entirely  satisfactory,  the  picture  is 
ready  for  release  printing. 

Producing  companies  usually  have  a  production  laboratory  in  the 
vicinity  of  the  studio  and  a  release  laboratory  at  the  distribution 
center.  The  second  sample  print  is  sent  immediately  upon  comple- 
tion to  the  release  laboratory,  together  with  the  sound  and  picture 
negatives.  This  permits  the  distributing  officials  to  inspect  the 
picture  before  making  the  release  prints. 


The  negatives  can  be  timed  and  the  proper  printer  step  on  which 
to  expose  a  given  negative  can  be  determined  by  inspecting  the 
negative.  An  experienced  timer  can  determine  the  step  on  which 
the  negative  should  be  exposed  in  order  to  obtain  a  high  quality 
print  simply  by  inspecting  the  density  of  the  negative.  However, 
most  laboratories  also  use  an  exposing  device,  either  for  the  purpose 
of  checking  the  timer  or  for  use  in  emergencies.  Such  a  device  is  so 
constructed  as  to  obtain  simultaneously  a  series  of  exposures  that 
match,  respectively,  points  over  the  entire  printer  scale.  Thus, 
a  negative  can  be  timed  by  printing  in  such  a  device,  and  developing, 
this  short  sample  strip.  The  proper  step  can  then  be  easily  deter- 
mined by  inspection.  As  was  mentioned  in  connection  with  the 
developer,  the  timer  must  also  be  advised  of  the  lighting  effects  in  the 
picture  that  the  cameraman  is  attempting  to  obtain. 

Most  negatives,  notwithstanding  the  careful  handling  in  air 
conditioned  rooms,  require  a  thorough  cleaning  before  printing. 
Several  simple  cleaning  devices  have  been  tried  and  some  are  still 
in  use.  Most  negatives,  however,  are  still  cleaned  by  hand  with 
carbon  tetrachloride.  Both  sides  of  the  film  are  firmly  wiped  with  a 
saturated  pad  of  velvet  or  some  other  soft  cloth.  As  the  vapor  of 
carbon  tetrachloride  is  unpleasant,  drafts  are  provided.  The  vapor 
is  heavier  than  air,  so  down  drafts  are  recommended.  The  fre- 
quency of  cleaning  necessary  during  printing  depends  upon  the  main- 
tenance of  the  rooms  and  machines.  Usually  the  negatives  are 
cleaned  after  a  dozen  prints  have  been  made. 

In  some  laboratories,  the  printers  are  fitted  with  suction  devices 
for  cleaning  the  raw  stock.  Dust  particles  or  any  other  particles  that 

196  CARE  AND  DEVELOPMENT  OF  FILM         [J.  S.  M.  P.  E. 

might  have  been  deposited  upon  the  emulsion  are  removed.  The 
illumination  of  the  modern  printing  room  is  more  than  sufficient  for 
efficient  machine  operation.  Properly  filtered  light,  and  white  walls, 
can  provide  satisfactory  uniform  illumination  without  fear  of  fogging. 

Two  types  of  printers  are  employed  in  picture  printing:  step 
printers  and  continuous  printers.  The  laboratories  using  step 
printers  claim  that,  due  to  the  better  contact,  the  definition  obtained 
on  such  printers  is  superior  to  that  obtained  on  continuous  printers. 
Those  using  continuous  printers  may  or  may  not  admit  this  ad- 
vantage of  the  step  printer,  but  they  state  that  .the  increased  speed 
and  the  ability  to  print  either  sound  or  picture  more  than  com- 
pensate for  a  small  loss  of  definition.  Step  printers  run  at  rates 
varying  from  20  to  70  feet  of  film  per  minute,  while  continuous 
printers  operate  at  65  to  100  feet  per  minute.  The  number  of  breaks, 
the  damage  caused  by  a  break,  and  the  wear  and  tear  on  the  negative 
increase  with  the  speed  of  printing. 

Approximately  half  the  laboratories  have  adapted  their  printers  to 
permit  the  simultaneous  printing  of  sound  and  picture  films.  This 
requires  a  second  printing  aperture  and  light  source,  as  well  as  addi- 
tional incidental  equipment.  Some  few  machines  have  been  modified 
to  permit  forward  and  backward  printing. 

For  newsreels,  both  picture  and  sound  are  printed  on  continuous 
machines.  Usually  the  picture  is  printed  first,  the  sound  being 
properly  displaced  and  printed  after  rewinding.  The  newsreel 
negative  is  cut  into  lengths  of  approximately  one  hundred  feet. 
This  permits  a  number  of  printing  machines  to  be  used,  and  consider- 
ably decreases  the  time  of  printing. 


Many  methods  of  duplicating  can  be  found  in  practice.  Special 
duplicating  stocks  have  been  manufactured  to  aid  the  laboratories  to 
produce  duplicate  negatives  that  are  exact  replicas  of  the  original 

A  positive  emulsion  with  a  lavender  base  is  most  commonly  used 
for  master  positives.  The  colored  base  serves  to  identify  the  emul- 
sion, and  acts  as  a  filter  when  the  duplicate  negative  is  exposed. 

A  special  negative  duplicating  emulsion  is  made,  which  incorporates 
a  yellow  dye.  The  effect  of  the  dye  is  to  retard  the  penetration  of 
the  light,  and  to  cause  the  image  to  be  maintained  on  the  surface 
of  the  emulsion. 

Mar.,  1933]  LABORATORY  PRACTICE  197 

In  some  instances,  regular  positive  stock  is  used  for  both  master 
positives  and  duplicate  negatives,  whereas  in  other  laboratories 
the  duplicate  negative  emulsion  is  used  for  both  purposes.  When 
the  identical  emulsion  is  used  for  master  positives  and  duplicate 
negatives,  it  receives  equal  development  in  each  case.  Since  the 
development  gamma  product  of  the  master  positive  and  the  duplicate 
negative  should  lie  in  the  range  0.90  to  1.00  in  order  to  reproduce 
correctly  the  original  negative,  the  respective  development  gammas 
are  approximately  0.95. 

The  latest  experimental  results  indicate  that  the  highest  quality 
duplicates  are  obtained  by  using  the  lavender  duplicating  positive 
and  the  yellow-dyed  duplicating  negative.  The  former  is  developed 
in  a  positive  bath  to  a  gamma  of  1.80  to  1.90,  and  the  latter  is  de- 
veloped in  a  borax  negative  bath  to  a  gamma  of  0.50  to  0.60. 

In  picture  duplicating,  step  printers  are  frequently  used.  Fast 
printing  is  unnecessary,  and  losses  of  definition  are  cumulative. 
Excellent  duplicates  have  been  obtained,  however,  on  both  step  and 
continuous  printers. 

Sound  records  can  be  successfully  duplicated  in  the  same  manner 
as  a  picture.  Many  companies  prefer  to  re-record  the  sound,  as  a 
small  percentage  of  the  high  frequencies  is  lost  in  printing,  due  to  poor 
contact  and  slippage.  In  re-recording,  it  is  possible  to  equalize  any 
desired  portion  of  the  frequency  range. 


Numerous  systems  are  advocated  for  treating  release  prints  chemi- 
cally or  physically  in  order  to  increase  the  life  of  the  prints  and  elimi- 
nate projection  difficulties.  When  new  prints  are  projected  there 
is  a  strong  tendency  for  the  emulsion  to  deposit  on  the  tension  shoes 
or  aperture  plate  of  the  projector.  The  result  is  that  abnormal 
forces  are  caused  to  act  on  the  perforations,  and  the  film  may  be 
seriously  damaged.  As  this  difficulty  disappears  after  the  print  has 
been  projected  several  times,  it  is  desirable  to  treat  the  new  prints 
by  some  method  that  will  give  them  the  same  characteristics  as 
prints  that  have  been  projected  a  number  of  times. 

In  one  system  the  gelatin  is  caused  to  swell,  thus  permitting  to  be 
introduced  into  it  substances  that  harden  the  surface  and  cause  a 
glossy  finish.  After  receiving  such  a  treatment  the  film  is  supposed 
to  be  able  to  resist  successfully  any  normal  mechanical  attacks. 
This  method  of  seasoning  requires  special  laboratory  equipment,  or 


the  film  must  be  sent  to  a  seasoning  laboratory.  Several  other 
systems,  claimed  to  effect  the  same  results,  involve  a  patented 
solution  which  is  added  to  the  fixing  bath. 

Although  some  of  these  systems  appear  to  have  merit,  most  of  the 
laboratories  are  content  with  edge  waxing  and  buffing.  Sometimes 
the  buffing  is  omitted,  the  edge  waxing  being  done  automatically  as 
the  film  emerges  from  the  drying  cabinets. 

R.  F.  NICHOLSON,  Chairman 
R.  C.  HUBBARD,  Vice- Chairman 








The  following  report,  reviewing  the  conditions  as  actually  found  at  present  in  the 
field,  is  intended  as  an  introduction  to  a  more  detailed  and  technical  study  of  exchange 
practice  to  be  reported  on  later.  All  the  phases  of  handling  film  in  the  exchanges  are 
discussed,  beginning  with  the  reception  of  the  release  print  from  the  laboratories, 
passing  through  treating  and  processing,  maintenance  and  inspection,  and  including 
a  discussion  of  the  equipment  and  control  of  the  exchanges.  Following  the  initial 
work  of  the  sub-committee,  represented  by  studies  of  the  existing  conditions  described 
in  this  report,  the  sub-committee  purposes  in  future  reports  to  deal  separately  and  at 
great  length  with  each  of  these  phases  individually. 


A .  Introduction 

B.  Laboratory  practice 

(1)  Standard  release  print 

(2)  Treating  and  processing 
(5)     Capacity  of  reels 

(4)  Footage  of  reels 

(5)  Mounting  of  film 

C.  Exchange  practice 

(1)  Maintenance  of  film 

(2)  Storing  of  film 

(5)  Shipping  routines  and  records 

(4)  Housekeeping,  and  control  of  fire  hazards 

(5)  Equipment 

(6)  Home  office  control 


Introduction.  In  this,  the  first  report  of  the  Sub-committee  on  Exchange 
Practice,  only  some  few  definite  recommendations  to  the  entire  industry  are 
made.  Included  in  the  report,  however,  are  numerous  suggestions  that  should 
prove  valuable  when  individual  practice  permits  their  application. 

Laboratory  Practice.  Many  difficult  problems  in  exchange  practice  could  be 
completely  obviated  if  all  laboratory  work  were  correct  and  complete.  Proper 
seasoning  of  the  film  after  developing  would  increase  the  life  of  the  print.  A  more 
uniform  picture  density  and  sound  volume  are  highly  desirable. 

Maintenance  of  Film.  New  film  received  by  the  exchanges  should  be  mounted 
on  perfect  reels  and  properly  identified.  All  film  should  be  inspected  and  repaired 


200  CARE  AND  DEVELOPMENT  OF  FILM         [j.  s.  M.  P.  E 

immediately  upon  its  return  from  the  theater.  A  complete  record  should  be 
kept  of  the  condition  of  each  reel  of  film. 

Storing  of  Film.  Film  should  be  stored  according  to  the  code  of  the  National 
Board  of  Fire  Underwriters,  and  all  local  Boards.  Temperature  and  humidity 
should  be  controlled  wherever  possible. 

Shipping  Routines  and  Records.  All  movements  of  film  should  be  recorded. 
A  more  uniform  method  of  keeping  records  throughout  the  various  exchanges 
should  prove  advantageous. 

Housekeeping  and  Control  of  Fire  Hazards.  The  National  Board  of  Fire 
Underwriters  and  the  Department  of  Conservation  of  the  Motion  Picture  Pro- 
ducers and  Distributors  of  America  have  formed  rules  for  the  handling  of  film. 
These  rules  should  be  strictly  adhered  to  by  the  film  exchanges. 

Equipment.  The  desirable  types  of  rewind  splicers  and  other  equipment  are 
listed.  Automatic  splicing  machines  have  been  found  to  be  more  satisfactory 
than  the  hand-operated  splicing  device. 

Home  Office  Control.  Proper  home  office  control  of  exchange  office  routines 
produces  satisfactory  results. 


In  view  of  the  fact  that  the  film  exchanges  are  inadequately  repre- 
sented in  the  membership  of  the  Society,  considerable  research  work 
outside  the  membership  of  the  sub-committee  was  found  necessary, 
in  order  to  obtain  information  on  the  operating  routines  of  some  of 
the  exchange  units  of  the  industry. 

In  the  following  report,  laboratory  practice  and  projection  practice 
have  been  touched  upon  only  so  far  as  was  thought  necessary  to 
correlate  the  work  of  those  phases  of  the  industry  and  that  of  ex- 
change practice.  Those  phases  include  the  preparation,  by  the 
laboratory,  of  the  release  print  for  the  exchange,  and  the  control  by 
the  exchanges  of  the  film  while  in  the  hands  of  the  projectionist. 


(1)  Standard  Release  Print. — By  adopting  the  standard  release 
print,  the  laboratories  have  vacated  many  of  the  irregularities  that 
formerly  confronted  the  exchanges,  but  there  yet  remain  other  prob- 
lems to  be  solved  with  the  aid  of  the  laboratories.  The  variations 
of  the  volume  range  of  sound,  and  of  the  density  of  the  printed  image 
of  both  the  sound  and  the  picture,  are  purely  laboratory  problems 
in  so  far  as  printing  is  concerned,  although  they  contribute  seriously 
to  the  difficulties  of  the  exchanges  for  the  reason  that  such  irregulari- 
ties are  rarely  evident  until  the  first  screening  of  the  print  in  the 
theater,  when  insufficient  time  remains  in  which  to  obtain  a  replace- 
ment print.  Standardization  by  the  laboratories  in  this  respect  is 
highly  desirable. 

Mar.,  1933]  EXCHANGE  PRACTICE  201 

(2)  Treating  and  Processing. — When  preparing  a  print  for  the 
exchange,  it  is  desirable  that  the  laboratory  treat  it  so  that: 

(1)  The  pulling  or  straining  of  perforations,  due  to  deposits  of  emulsion  on 
the  tension  shoes  or  aperture  plate  of  the  projector  be  eliminated. 

(2)  The  emulsion  be  so  toughened  as  to  resist  scratching  of  the  surface  of 
the  film  as  far  as  possible. 

(3)  The  warping  and  buckling  of  the  film,  caused  by  the  heating  of  the  gelatin 
by  the  projection  lamp,  should  be  reduced  as  far  as  possible. 

(4)  The  pliability  of  the  gelatin  and  its  binder  should  be  as  permanent  as 
possible,  so  that  the  useful  life  of  the  film  may  be  made  at  least  equal  to  the 
booking  period. 

(3)  Capacity  of  Reels. — A  standard  size  of  reel,  agreed  to  and 
used  by  both  the  exchanges  and  the  projectionists,  must  be  adopted 
for  the  good  of  all  concerned.  The  mounting  of  film  in  the  exchanges 
on  1000-foot  reels  for  transportation,  the  subsequent  transferring  of 
the  film  to  reels  holding  from  1500  to  3000  feet  of  film  in  the  projec- 
tion room,  and  the  re-transfer  to  the  original  1000-foot  reels  for  re- 
turn to  the  exchange  represents  a  great  deal  of  lost  motion.  Need- 
less time  and  effort  is  spent  by  the  projectionist  in  making  such 
changes.  A  like  amount  of  time  and  effort  is  lost  in  the  exchange 
inspection  room  in  checking  the  correctness  of  the  footage  and  of  the 
heads  and  tails  of  the  reels. 

A  large  amount  of  film  footage  is  lost  because  of  this  practice, 
and  either  all  film  should  be  mounted  on  large  reels  in  the  exchanges, 
or  projectionists  should  be  forced  to  discontinue  the  practice  of 
mounting  two  or  more  reels  of  film  on  one  large  reel. 

From  an  exchange  standpoint,  the  1000-foot  reel  is  far  more  desir- 
able, owing  to  the  greater  ease  with  which  it  can  be  handled  and  the 
greater  efficiency  with  which  it  can  be  inspected. 

The  tensile  strength  of  new  film  and  its  elongation  properties  will 
permit  reels  to  be  doubled  under  proper  working  conditions  without 
damaging  the  film;  but  when  the  film  has  become  seasoned  the 
perforation  area  admits  of  less  elongation  than  the  center  of  the 
film  and  is,  therefore,  subjected  to  the  entire  strain  of  the  traction 
load  of  the  film  in  the  upper  and  lower  magazines. 

The  braking  surface  in  the  upper  magazine,  for  properly  controlling 
the  feed  of  the  film  when  the  double  reel  is  full,  causes  a  tension  to  be 
applied  to  the  later  footage  of  the  reel  that  often  is  greater  than  the 
elongation  of  the  perforation  area  permits.  The  perforations,  as  a 
result,  break  down. 

In  the  lower  magazine,  improper  adjustment  of  the  friction  drive 

202  CARE  AND  DEVELOPMENT  OF  FILM         [J.  S.  M.  P.  E. 

or  the  take-up  will  often  cause  a  similar  condition  in  the  early  footage 
of  a  reel.  The  variation  of  the  shaft  speed  of  the  take-up,  caused  by 
the  increasing  of  the  circumference  of  the  reel  as  footage  is  added  to 
it,  is  compensated  for  in  a  friction  drive  that  must  be  precisely  ad- 
justed to  drive  the  take-up  steadily  when  the  reel  is  filled.  The 
friction  required  to  cause  such  a  steady  drive  of  a  full  reel  is  greater 
than  that  required  for  the  incomplete  reel;  whence  there  results  a 
tendency,  in  the  early  footage,  for  the  reel  to  take  the  film  faster  than 
it  is  fed  out  by  the  lower  sprocket. 

Insufficient  tension  on  the  friction  drive  of  the  take-up  will  halt 
the  loaded  reel  momentarily,  thus  creating  a  slack  in  the  film  between 
the  take-up  reel  and  the  lower  sprocket.  This  slack  permits  the 
take-up  drive  to  operate  under  no  load,  and  the  reel  accelerates 
ahead  of  the  feed  of  the  lower  sprocket,  tearing  the  film  at  the  lower 
sprocket  when  the  end  of  the  slack  is  reached. 

Suggesting  a  remedy  for  this,  the  sub-committee  believes  that  it 
would  be  well  for  the  exchanges  to  consider  mounting  all  film  on  1000- 
foot  reels  having  5-inch  hubs,  instead  of  on  the  1000-foot  reels  with 
the  2-inch  hubs  now  universally  used  by  the  exchanges. 

Because  of  the  larger  hub,  the  reel  can  be  made  considerably 
stronger,  and  a  more  positive  stand  can  be  consistently  taken  against 
the  doubling  of  reels  by  the  projectionists.  Such  a  reel  would 
vacate  two  of  the  faults  of  the  reel  now  generally  used  by  the  ex- 
changes that  most  projectionists  offer  as  reasons  for  doubling  reels: 
namely,  a  uniform  reel  for  use  in  the  upper  magazine,  and  a  reel  with 
a  5-inch  hub  for  the  take-up  in  the  lower  magazine.  This  size  of 
reel  could  be  used  without  materially  changing  the  present  shipping 
cases,  vault  racks,  or  equipment  in  the  inspection  rooms. 

The  cost  of  a  strongly  built  reel  with  a  5-inch  hub  would  be  greater 
than  that  of  the  reel  now  used;  but  it  is  the  opinion  of  the  sub- 
committee that  this  difference  in  cost  would  be  more  than  offset  by 
the  probable  saving  of  time  of  inspection,  the  elimination  of  doubling 
of  reels,  and  the  loss  of  film  at  the  beginnings  and  ends  of  the  reels. 

(4)  Footage. — The  footage  of  a  reel  is  usually  dependent  upon  the 
editing  of  the  picture,  and  can  not  be  controlled  by  the  laboratory; 
but  if  a  standard  approximate  length  were  subscribed  to  and  adopted 
by  the  exchanges  and  the  laboratories,  the  film  cutter  could  be  in- 
duced to  restrict  his  editing  accordingly.  A  desirable  footage  under 
the  present  exchange  operating  conditions  would  be  approximately 
950  feet  per  reel,  a  maximum  being  set  at  1000  feet. 

Mar.,  1933]  EXCHANGE  PRACTICE  203 

The  matter  of  mounting  film  on  metal  reels  in  the  laboratory  before 
shipping  to  the  exchanges,  and  the  shipping  of  film  in  metal  I.  C.  C. 
shipping  cases  instead  of  in  the  wooden  cases  now  used,  can  be  re- 
garded from  many  points  of  view.  If  all  film,  other  than  newsreel 
releases,  were  mounted  on  reels  at  the  laboratory,  new  reels  far  in 
excess  of  the  number  now  bought  by  the  exchanges  would  have  to  be 
purchased,  or  the  return  of  used  reels  by  the  exchanges  to  the  labora- 
tories on  the  obsolescence  and  dismantling  of  film  would  have  to 
be  insisted  upon.  Such  a  practice  would  not  offer  sufficient  ad- 
vantages to  make  it  worth  while  to  propose  it  as  a  standard  of  general 

Shipping  Cases. — In  the  matter  of  containers  for  shipments:  the 
cost  of  the  wooden  cases  now  used  for  shipping  film  from  the  labora- 
tories to  the  exchanges  is  written  off  after  the  initial  shipment  is 
received  by  the  exchange,  as  these  cases  have  no  further  value. 
The  greater  weight  of  the  metal  I.  C.  C.  shipping  case,  if  used, 
would  increase  the  carrying  charge  on  the  initial  shipment  so  that  it 
would  equal  the  cost  of  the  wooden  case.  The  practice  of  shipping 
releases  in  metal  I.  C.  C.  cases  would  make  it  necessary  to  return  the 
cases  to  the  laboratory  when  final  disposition  of  the  film  at  the  ex- 
change is  made.  If  a  reclamation  plant  were  established,  to  which  all 
I.  C.  C.  cases  could  be  sent  by  all  exchanges  after  final  disposition  of 
the  film,  a  considerable  saving  could  be  effected  for  the  industry,  as  a 
large  percentage  of  the  metal  cases  now  junked  by  the  exchanges 
because  of  the  lack  of  means  of  repairing  them  could  be  repaired  at 
such  a  plant  for  a  small  fraction  of  the  initial  cost.  They  could  then 
be  allotted  to  the  various  laboratories  for  subsequent  shipments  of 
new  film  to  the  exchanges.  Such  an  arrangement  would  require  a 
repair  plant  at  both  New  York  and  Hollywood,  and  cases  could  be 
sent  by  the  exchanges  to  either  plant  by  freight  or  express.  A  carry- 
ing charge  of  20  cents  would  be  levied  on  each  case  sent  from  any 
point  in  the  United  States,  the  express  company  making  a  return 
charge  of  20  cents  for  any  container  in  which  an  original  shipment  was 
made  by  express. 

(5)  Mounting. — When  film  is  mounted  on  reels  at  the  laboratory, 
film  bands  bearing  the  title  of  the  subject  and  the  number  of  the 
reels  should  be  stamped  thereon.  When  unmounted,  it  is  desirable 
that  the  reels  be  wound  with  the  "tails"  outward.  A  standard 
size  of  flange  should  be  used  by  both  laboratories  and  exchanges  for 
mounting  or  dismounting  film. 

204  CARE  AND  DEVELOPMENT  OF  FILM         [J.  S.  M.  P.  E. 


Exchange  practice  involves  the  routine  handling  of  film  during  its 
exhibition  life,  and  usually  it  would  appear  as  though  most  of  the 
exchanges  followed  in  the  main  the  same  operating  procedure.  A 
comparison  of  the  condition  of  the  film  of  one  distributor  or  ex- 
change with  that  of  another  shows  that  such  is  not  the  case,  and 
demonstrates  the  need  of  standardizing  the  operating  technic  of  all 
exchanges  of  all  companies. 

In  assembling  the  information  obtained  from  the  various  distribu- 
tors on  the  routine  care  and  maintenance  of  film,  the  sub-committee 
has  endeavored  to  select  and  suggest  for  general  adoption  those 
features  thought  most  amenable  to  standardization.  Distributing 
companies  that  maintain  their  film  in  the  best  condition  are  those 
that  are  completely  controlled  by  their  home  offices.  It  seems  to  be 
desirable  that  all  distributing  companies  be  similarly  controlled. 
The  home  office,  through  its  control,  should  direct  the  routines  of  the 
exchanges  in  respect  to  what  is  described  in  the  remainder  of  this 
report,  and  should  hold  the  exchange  managers  responsible  for  the 
adherence  of  the  exchange  to  the  policies  instituted. 

(1)  Maintenance  of  Film. — Film  received  from  the  laboratory 
should  be  mounted  on  new  reels  or  on  reels  that  are  in  perfect  condi- 
tion. A  flange  made  for  the  specific  purpose  should  be  used  and 
film  bands  bearing  complete  information  should  be  placed  around  the 
film.  Film  should  never  be  mounted  from  a  flat  table,  or  from  a 
makeshift  flange  made  from  old  reels.  Under  no  conditions  should  a 
pencil  or  other  wooden  rod  ever  be  used  as  a  hub  or  spindle  in  the 
center  of  the  reel  of  film,  as  a  positive  fire  hazard  is  created  by  the 
friction  of  the  film  rubbing  against  the  wood. 

A  film  record  card  should  be  made  out  for  each  print,  on  which  is 
kept  a  record  of  the  condition  of  the  film,  its  location  while  in  the 
vaults,  full  data  on  playing  dates  while  out  of  the  house,  the  in- 
spector's initials,  and  the  date  of  each  inspection. 

Film  should  be  graded  as  to  its  condition  in  the  following  manner: 

No.  1  condition:  good  in  every  respect. 
No.  2  condition:  good;  film  damaged  slightly. 
No.  3  condition:  film  in  poor  condition. 
No.  4  condition:  junk  film. 

As  this  manner  of  grading  film  specifies  film  that  would  be  acceptable 
in  any  first-class  theater  as  in  No.  1  condition,  and  film  unfit  for  use 
as  in  No.  4  condition,  the  range  of  conditions  between  No.  1  and 

Mar.,  1933]  EXCHANGE  PRACTICE  205 

No.  4  is  very  wide.  New  film  can  be  graded  only  as  No.  1 ,  and '  'junk' ' 
film  can  be  graded  only  as  No.  4;  whence  it  follows  that  No.  2  film 
is  considered  to  be  good  film,  but  its  acceptance  in  a  class  "A"  house 
would  be  questionable.  Therefore,  it  is  considered  good  film  until 
the  inspector  finds  out  otherwise  and  marks  it  as  "3,"  meaning  in 
poor  condition.  Dirt  and  oil  on  the  film  should  not  be  considered  in 
grading  the  film,  as  obviously  any  grade  of  film  can  be  dirty  or  oily, 
but  be  restored  to  the  proper  condition  by  cleaning  or  process- 
ing. The  sub-committee  feels  that  it  is  desirable  for  every  ex- 
change to  have  available  a  place  where  dirty  and  oily  film  can  be 

Film  can  be  satisfactorily  cleaned  by  cleaning  machines  now  on  the 
market.  If  done  in  the  exchange,  it  is  impracticable  to  attempt  to 
clean  film  by  hand.  All  cleaning  fluids  should  be  non-inflammable 
and  uninjurious  to  celluloid  or  gelatin.  Carbon  tetrachloride  can  be 
used  satisfactorily  for  cleaning  film,  as  can  trichlorethylene,  but  the 
use  of  either  requires  proper  ventilation. 

For  exchanges  that  would  operate  their  own  cleaning  plants,  the 
sub-committee  recommends  the  use  of  a  machine  that  submerges  the 
film  in  the  cleaning  fluid,  cleans  the  emulsified  dirt  and  oil  from  the 
film  by  passing  the  film  through  a  series  of  soft  rubber  squeegees, 
and  polishes  it  by  passing  it  over  revolving  rollers  covered  with 
soft  flannel.  The  machine  and  the  room  should  be  well  ventilated. 

Film  should  be  inspected  and  repaired  immediately  upon  being 
returned  from  the  theater,  and  the  condition  of  the  film  should  be 
noted  and  recorded  on  the  "film  record  card."  When  undue  damage 
has  occurred  to  any  part  of  a  print,  the  record  card  should  carry  in- 
formation of  the  damage  and  the  name  of  the  theater  responsible  for 
it.  The  booking  manager  of  the  exchange  should  be  furnished  with 
complete  data  on  the  damage,  repairs  made,  and  the  replacement 
parts  ordered  when  necessary. 

Inspectors  should  not  be  permitted  to  wear  anything  on  their  hands 
other  than  a  light  cotton  glove.  While  inspecting  film,  all  jewelry 
should  be  removed  from  fingers  and  wrists. 

All  film  should  be  inspected  from  the  left  rewind  to  the  right,  be- 
ginning with  the  "tail"  of  the  reel  outward,  so  that  the  inspected  film 
reel  ends  on  the  right-hand  rewind  with  the  "start"  or  head  of  the 
reel  outward.  As  all  splices  are  made  by  scraping  the  film  on  the 
left  of  the  damaged  part,  this  routine  results  in  a  splice  that  is  better 
fitted  to  pass  through  the  curves  and  loops  and  over  the  sprockets  of  a 

206  CARE  AND  DEVELOPMENT  OF  FILM         [J.  S.  M.  P.  E. 

Simplex  projector.  In  splicing,  the  emulsion  should  be  removed  with 
a  dry  scraper.  Only  fresh  film  cement  should  be  used.  A  mechani- 
cal splice  is  recommended,  and  should  always  be  referred  to  as  a 
"splice"  and  not  as  a  * 'patch." 

The  inspector  should  hold  the  film  so  that  it  passes  first  over  the 
left  hand  and  then  between  the  fingers.  If  held  so  that  the  film  passes 
under  the  left  hand  before  passing  through  the  fingers,  all  the  dirt  and 
grit  that  is  on  the  film  collects  on  the  palm  of  the  hand  and  scratches 
the  remainder  of  the  reel  being  inspected. 

In  order  to  maintain  the  proper  locations  of  the  "change-over" 
signals  in  the  standard  release  print,  where  these  have  been  altered 
by  placing  the  film  on  2000-foot  reels,  the  "start"  mark  should  always 
be  placed  at  the  correct  distance  ahead  of  the  action.  This  distance 
should  be  exactly  determined  in  all  reels  of  all  prints,  and  can  be 
maintained  by  the  film  footage  numbers  in  the  margin  of  the  film. 
When  necessary,  black  leader  film  should  be  inserted  between  the 
"start"  mark  and  the  first  scene  of  the  action  in  order  to  maintain 
the  correct  distance. 

When  splices  occur  at  the  ends  of  reels,  shortening  the  distance 
between  the  "start-motor"  signal  or  the  "cut-over"  signal  and  the 
end  of  the  action,  replacement  film  should  be  inserted;  or  the  "start- 
motor"  signal  or  the  "cut-over"  signal  should  be  removed,  making 
new  ones  at  the  proper  distance  from  the  end  of  the  action  in  order  to 
provide  the  projectionist  with  the  correct  "cut-over"  cues.  To  avoid 
mutilation  of  the  film  by  punch  marks,  stickers,  and  scratches,  ex- 
changes should  notify  all  exhibitors  that  the  only  permissible  way 
of  indicating  variations  from  the  standard  release  print  markings 
would  be  to  use  a  china  marking  pencil,  and  that  such  marks  should 
not  extend  over  two  frames. 

The  inspector  should  examine  the  marginal  footage  numbers  on 
both  sides  of  each  splice  when  inspecting  sound  film,  so  as  to  deter- 
mine the  probable  deletion  of  footage.  If  the  deletion  is  large  or  im- 
portant, replacement  film  is  necessary.  Companies  that  do  not  ad- 
here to  a  distinctive  uniform  splice  should  require  that  each  splice 
made  and  examined  be  stamped  with  an  embossing  stamp  to  signify 
that  the  footage  deleted  has  been  "okayed."  This  precludes  the 
necessity  of  a  like  examination  in  following  inspections. 

The  inspection  should  be  supervised  by  a  person  well  informed  in 
the  work,  who  should  always  be  in  close  contact  with  the  booking 
department,  and  be  responsible  to  it  for  the  correct  maintenance  of 

Mar.,  1933]  EXCHANGE  PRACTICE  207 

the  film.    Care  should  be  exercised  by  the  personnel  department  as  to 
the  ability  of  persons  employed  to  inspect  film. 

Various  forms  are  necessary  in  every  inspection  department:  (a) 
an  individual  notebook,  maintained  by  each  inspector,  showing  the 
amount  of  work  done  daily,  the  production  number  or  title  of  each 
subject  inspected,  and  the  number  of  reels  and  their  condition. 
The  supervisor  should  determine  from  these  notebooks  the  amount  of 
work  done  each  day,  and  should  render  to  the  branch  manager  a 
weekly  report  showing  a  complete  resume  of  the  work;  (b)  forms  for 
reporting  damaged  film  to  the  booking  department,  to  be  filled  out  by 
the  inspector's  supervisor;  (c)  forms  for  ordering  replacement  parts, 
to  be  filled  out  by  the  inspector's  supervisor,  and  handed  to  the 
booking  department. 

(2)  Storing  of  Film. — Film  should  be  stored  only  in  sprinkler- 
equipped  vaults  or  cabinets  properly  vented,  and  built  in  accordance 
with  the  code  of  the  National  Board  of  Fire  Underwriters,  and  all 
local  fire  ordinances. 

Film  that  is  yet  in  its  booking  stage  should  be  filed  in  film  vaults  in 
the  I.  C.  C.  container  in  which  it  is  shipped  to  the  theater.  Film  to 
be  stored  permanently  should  be  removed  from  its  reels  and  filed  in 
individual  approved  containers.  The  sub-committee  recommends 
that  the  temperature  inside  the  vaults  be  kept  as  nearly  at  the 
temperature  of  the  shipping  room  as  is  possible  in  exchanges  through 
which  film  is  passing.  For  storing  and  preserving  film  permanently, 
the  temperature  of  the  air  should  be  maintained  approximately  at 
65°F.  to  70°F.  at  a  relative  humidity  of  65  per  cent. 

(3)  Shipping  Routines  and  Records. — The  shipping  and  receiving 
of  film  and  the  routine  used  in  these  connections  can  more  easily  be 
standardized  than  the  inspection  and  maintenance  of  film,  for  the 
reason  that  no  variations  occur  in  the  shipping  routines  found  in 
different  localities  or  in  small  or  large  exchanges.     All  movements  of 
film  are  recorded  on  the  "film  record  card."     No  film  of  any  footage 
whatsoever,  except  scrap  film,  should  be  sent  from  the  film  room 
without  an  order  from  the  person  or  department  authorized  to  make 
such  orders  directing  its  movement.     Scrap  film  should  be  delivered 
only  to  a  person  or  agency  duly  authorized  by  the  city  authorities  to 
collect  it,  and,  regardless  of  quantity,  should  never  be  burned  in  the 
basement  of  the  building  or  in  any  adjacent  lots. 

The  forms  used  in  shipping  and  receiving  film  should  include  a 
daily  shipping  sheet,  made  up  by  the  booking  department  and  ac- 

208  CARE  AND  DEVELOPMENT  OF  FILM         [J.  S.  M.  P.  E. 

companied  by  individual  shipping  orders  from  the  accounting  de- 
partment, shipping  labels,  caution  labels,  C.O.D.  labels  and  orders  for 
shipments  to  be  sent  C.O.D.,  express  delivery  records,  receiving 
records,  reports  for  overdue  film,  and  packing  slips  for  return  of 
"junk"  film. 

(4)  Housekeeping  and  Control  of  Fire  Hazards. — Conditions  and 
control  of  fire  hazards  in  both  inspection  and  shipping  rooms,  and 
in  the  vaults  of  an  exchange,  should  be  standardized  as  far  as  possible. 
The   sub-committee   recommends   that   the  rules   governing   these 
conditions,  as  laid  down  by  the  National  Board  of  Fire  Underwriters 
and  supported  throughout  and  followed  up  by  the  Department  of 
Conservation  of  the  Motion  Picture  Producers  and  Distributors  of 
America,  be  endorsed  by  the  S.  M.  P.  E.  and  recommended  as  stand- 
ards of  procedure  for  all  exchanges  of  all  companies.     The  Depart- 
ment of  Conservation  of  the  M.  P.  P.  D.  A.  has  been  following  this 
work  completely  and  thoroughly,  as  evidenced  by  the  almost  total 
elimination  of  losses  by  fire  in  exchanges  that  are  receiving  the 
benefits  of  systematic  inspection  by  that  organization. 

No  unauthorized  visitors  should  be  permitted  in  the  film  rooms 
of  an  exchange.  Delivery  boys,  projectionists,  and  messengers 
picking  up  film,  should  not  be  allowed  free  access  to  the  film 

(5)  Equipment. — All  equipment  used  in  maintaining  film  and  in 
shipping  and  storing  it  should  be  standardized  for  all  exchanges  as 
far  as  possible,  so  that  a  uniform  procedure  may  be  followed.     Requi- 
site equipment  of  film  inspection  rooms  consists  of  tables,  chairs, 
rewinds,  mounting  flanges,  splicing  blocks,  title  cabinet,  leader  cabi- 
nets, waste  film  containers,  trash  cans,  cement  bottles  and  spreaders, 
film  band  holders,  supervisors'  desks,  and  filing  cabinets. 

The  use  6f  automatic  splicing  machines  equipped  with  table  tops 
obviates  the  need  of  separate  tables.  Such  machines  are  desirable  be- 
cause of  the  greater  ease  and  satisfaction  that  results  from  using  them 
and  the  greater  volume  of  work  that  can  be  accomplished  with  them. 
Where  manually  operated  splicing  blocks  are  used,  all-metal  in- 
spection tables  and  adjustable,  form-fitting  chairs  are  recommended. 

A  standardized  rewind  for  all  exchanges  is  recommended.  It  is 
desirable  that  all  rewinds  be  equipped  with  brakes,  controlled  by  the 
knee  of  the  operator  or  by  the  handle  of  the  right-hand  rewind,  ar- 
ranged so  as  to  stop  both  rewinds  simultaneously  when  applied. 

Mounting  flanges  should  be  of  standard  uniform  size  so  that  the 

Mar.,  1933]  EXCHANGE  PRACTICE  209 

hole  in  the  center  of  the  unmounted  reel  will  always  fit  the  hub  of  the 

A  desirable  title  cabinet  is  one  built  on  the  order  of  a  chest  of 
drawers.  Each  drawer  should  be  approximately  two  inches  deep, 
studded  with  upright  movable  pegs  on  which  to  insert  the  titles  and 
their  corresponding  tags.  This  cabinet  should  be  kept  in  one  of  the 
film  vaults. 

Leader  cabinets  should  have  three  compartments  for  the  three 
different  kinds  of  leader  required  for  the  maintenance  of  film  footage. 
The  gates  or  apertures  through  which  the  film  leader  is  drawn  as 
needed  should  be  so  built  as  to  prevent  fire  from  passing  into  the 
cabinet.  Film  band  holders  may  be  of  any  type  of  wall  bracket. 

Waste  film  containers  should  conform  to  the  code  of  the  National 
Board  of  Fire  Underwriters. 

Cement  bottles  should  hold  no  more  cement  than  the  amount 
required  for  one  day's  work,  and  should  be  equipped  with  a  metal 
spreader  built  into  a  metal  stopper,  the  weight  of  which  keeps  the 
bottle  closed. 

The  supervisor's  desk  should  be  made  entirely  of  metal  and  should 
have  sufficient  drawer  capacity  for  keeping  all  records  when  not  in  use. 
Filing  cabinets  should  be  made  entirely  of  metal  and  should  have 
sufficient  capacity  for  filing  continuity  sheets,  records,  etc. 

The  equipment  of  the  film  shipping  room  should  consist  of  packing 
and  receiving  tables,  hand  trucks,  chairs,  waste  film  containers,  tools, 
shelves,  shipper's  desk,  filing  cabinets,  and  trash  cans. 

Packing  and  receiving  tables  should  be  strong  and  made  entirely 
of  metal.  They  should  not  be  higher  than  30  inches.  The  shelves 
should  be  sufficiently  strong  and  made  entirely  of  metal,  and  should 
have  sufficient  capacity  for  storing  all  cases  of  film  awaiting  shipment 
or  inspection.  Hand  trucks  should  be  made  entirely  of  metal  and 
should  be  equipped  with  rubber  tires.  The  shipper's  desk  and  chair 
should  be  made  entirely  of  metal,  the  former  having  sufficient  drawer 
capacity  for  keeping  all  records  when  not  in  use.  Filing  cabinets 
should  be  made  entirely  of  metal  and  should  have  sufficient  capacity 
for  maintaining  a  complete  file  of  film  record  cards,  showing  the  "in 
and  out"  movement  of  film,  and  for  filing  all  shipping  and  receiving 
records.  Waste  film  containers  should  conform  to  the  code  of 
the  National  Board  of  Fire  Underwriters,  and  should  be  kept  in  one 
of  the  vaults.  Trash  cans  should  be  of  the  usual  type,  having 
tightly  fitting  lids  or  covers.  Tools  of  sufficient  variety  to  enable 


the  shipper  to  repair  equipment  and  cases  properly  should  be 

(6)  Home  Office  Control. — The  practice  followed  by  the  film  ex- 
changes should  be  controlled  by  the  home  ofiices,  and  should  be 
made  to  conform  to  the  procedure  adopted  by  them.  The  exchange 
manager  should  see  that  the  routine  standardized  by  the  home  office 
is  rigidly  followed  in  his  exchange  by,  first:  the  adoption  of  the 
best  routines  for  the  maintenance  of  film  and  reporting  to  the  home 
offices  all  particular  conditions  pertinent  to  them;  and,  second,  the 
thorough  and  capable  following  up  of  the  procedure  by  the  home 
office,  so  that  the  national  routine  may  be  emended  or  altered  when 
better  methods  of  operation  are  developed  by  an  individual  exchange. 

Exchanges  should  render  weekly  reports  on  film  inspection.  When 
reports  are  compiled,  a  national  summary  is  obtained,  from  which 
each  exchange  may  be  judged  as  to  the  volume  of  work,  cost  of  in- 
spection, shipments,  and  amount  of  uninspected  film  in  the  vaults. 
Exchanges  should  also  report  all  fire  hazards  at  least  once  a  month, 
supplementing  the  monthly  report  made  by  the  Motion  Picture 
Producers  and  Distributors  of  America.  Traveling  auditors  from 
the  home  office  also  should  include  in  the  audit  of  each  exchange  an 
accurate  and  complete  description  of  all  fire  hazards. 

The  home  office  should  have  available  a  representative  who  is 
thoroughly  informed  in  film  maintenance  so  that  his  services  might 
be  furnished  to  an  exchange  when  needed.  The  control  by  the 
exchanges  of  the  care  of  film  while  in  the  hands  of  the  projectionist 
should  include  only  a  correct  record  of  the  condition  of  the  print 
furnished  to  the  theater  and  an  observation  of  its  condition  on  its 
return.  Such  records  assist  in  avoiding  controversies  over  damaged 
film  and  charges  rendered  to  the  theater  by  the  exchange. 

The  success  of  the  film  exchange  in  its  work  depends  upon  furnish- 
ing the  exchange  with  the  correct  equipment,  establishing  uniform 
standards  of  routine  in  all  exchanges,  and  control  by  the  home 
office  to  see  that  the  adopted  routine  is  carried  out. 




J.  H.  SPRAY 



Summary. — The  evolution  of  the  modern  high  fidelity  recorder,  from  the  rela- 
tively crude  apparatus  first  used  for  recording  when  sound  was  added  to  the  picture,  is 
traced;  beginning  with  the  telegraphic  recording  device  known  as  the  pallophoto- 
phone  developed  by  C.  A.  Hoxie,  passing  through  the  phono  film  devised  Forest, 
and  continuing  through  the  RCA  PR-1  and  PR-3  to  the  up-to-date  PR-4  variable 
width  recorder  embodying  the  latest  developments  for  maintaining  a  high  constancy 
of  speed  and  for  producing  recordings  of  the  highest  quality.  The  paper  describes 
the  new  model  recorder  and  film  phonograph,  and  the  application  of  these  to  dubbing 
and  re-recording,  both  on  35-mm.  and  16-mm.  film. 

From  the  time  that  Thomas  Edison  made  the  first  scratch  in  the 
foil-covered  cylinder  down  to  the  present  day,  the  words  quality  or 
fidelity  have  been  used  in  criticism  of  the  recordings  that  were  made, 
no  matter  what  method  was  used.  These  words  define,  perhaps,  a 
condition  of  pleasantly  or  satisfactorily  exciting  the  auditory  nerves 
in  a  manner  bearing  a  recognizable  relation  to  the  original  sound. 
It  is  highly  probable  that  with  Mr.  Edison's  first  recording,  the  tre- 
mendous impetus  that  he  received  from  having  accomplished  what 
was  heretofore  locked  in  the  fastness  of  the  unknown,  caused  him  to 
rejoice  in  the  discovery  that  he  had  made.  It  is  a  historic  fact  that 
Mr.  Edison  and  his  co-workers  gave  some  thought  at  that  time  to 
one  feature  of  recording  that  in  this  day  and  age  has  become  of 
paramount  importance.  This  feature  was  partially  obscured  by  the 
fact  that  he  had  "re-created,"  in  the  form  of  a  permanent  or  semi- 
permanent record,  an  audible  sound  that  once  had  been,  and  could 
be  no  more. 

As  the  art  of  recording  progressed,  all  the  individuals  connected 
with  it  came  to  realize  that  the  attainment  of  good  quality,  as  regards 
the  frequency  composition  of  sound,  was  one  of  the  greatest  problems 
confronting  them.  But  quality  was  found  to  have  a  wider  scope,  and 
to  include  a  definite  relation  between  the  frequency  characteristic 
and  the  constancy  of  speed  maintained  while  recording  and  reproduc- 

*  Received  February  15,  1933. 
**  Engineering  Department,  RCA  Victor  Co.,  Camden,  N.  J. 


212  A.  G.  ZIMMERMAN  [j.  S.  M.  P.  E. 

ing  the  sound.  As  in  all  developments  of  this  nature,  the  past  efforts, 
when  reviewed  at  some  later  time,  were  considered  to  be  poor  replicas 
of  what  had  been  recorded,  and  served  to  emphasize  the  achievements 
accomplished  during  the  interim. 

The  progression  from  the  cylinder  to  the  disk  type  of  record  brought 
with  it  considerable  advantages,  both  from  the  commercial  and  from 
the  technical  standpoint,  when  the  increase  in  the  linear  speed  was 
considered  as  well  as  the  creation  of  a  more  flexible  product.  This 
advance  brought  with  it  a  wider  field  for  the  sale  of  records  and  repro- 
ducing machines  or  phonographs. 

Departing  from  the  field  of  quality  with  respect  to  the  frequency 
standpoint  and  considering  only  the  question  of  constancy  of  speed,* 
it  is  very  probable  that  since  the  conception  of  the  phonograph  down 
to  the  present  day,  millions  of  dollars  have  been  spent  by  firms  en- 
gaged in  the  original  recording  of  phonograph  records  for  sale,  by 
others  engaged  in  marketing  reproducing  machines,  by  engineers, 
and  other  individuals  too  numerous  to  mention  who  were  privately 
interested  in  solving  the  problem  of  speed  constancy.  Undeniable 
strides  were  made  in  reducing,  to  a  tolerable  limit,  the  variation  of 
speed  that  occurs  in  recording  and  reproducing  equipment  of  the 
phonograph  type. 

Mr.  C.  A.  Hoxie,  of  the  General  Electric  Company,  conceived  the 
idea  of  a  telegraphic  recording  device  that  would  enable  a  telegraph 
company  to  receive  telegraphic  communications  at  high  speed  on  a 
continuous  paper  film  and  to  preserve  them  for  their  records.**  As 
soon  as  this  device  had  been  created  and  so  improved  as  to  be  able  to 
record  messages  at  speeds  previously  considered  impossible,  the 
ever  alert  engineering  instincts  of  the  men  responsible  for  this  de- 

*  Inconstancy  of  speed  results  in  variations  usually  termed  wows  when  they 
have  a  frequency  below  10  cycles  per  second;  flutter  up  to  50  cycles,  and  gurgle 
above  50  cycles.  The  frequency  of  the  gurgle  is  usually  dependent  upon  the 
number  of  sprocket  teeth  engaging  the  film. 

**  A  historical  point  worthy  of  mention  is  the  fact  that  the  original  sensitized 
paper  film  recorder  was  developed  to  record  the  telegraphic  signals  when  trans- 
mitted at  the  usual  maximum  speed  of  25  to  35  words  per  minute.  Concurrently 
with  the  development  of  the  recorder,  the  possibility  of  increasing  the  speed  was 
apparent,  and  during  the  winter  of  1918  and  1919  a  Hoxie  telegraphic  recorder 
was  operated  at  Otter  Cliffs,  Bar  Harbor,  Maine,  handling  traffic  from  Lyons, 
France,  at  an  average  speed  of  50  words  per  minute.  Further  developments  and 
tests  demonstrated  the  ability  of  this  type  of  equipment  to  receive  as  many  as  250 
words  per  minute. 

Mar.,  1933]  FILM  RECORDERS  213 

velopment  conceived  the  idea  that  not  only  telegraphic  messages, 
requiring  only  the  comparatively  simple  dot-dash  method  of  record- 
ing, but  other  sounds,  such  as  the  human  voice  and  music,  could  be 
recorded  on  a  piece  of  film,  which  could  be  processed  and  reproduced. 

In  1922,  Mr.  Hoxie  developed  what  is  now  known  to  the  industry 
as  the  pallophotophone*  which  he  described  in  detail  at  the  Mid- 
Winter  Convention  of  the  A.I.E.E.  in  New  York  in  1923. 

The  success  of  Mr.  Hoxie's  trials  and  demonstrations  of  the  pallo- 
photophone immediately  created  an  impression  on  the  minds  of 
interested  persons  that  the  era  of  talking  pictures  was  definitely  at 
hand.  Dr.  Lee  de  Forest's  demonstration  of  the  phonofilm  at  ap- 
proximately the  same  time  also  contributed  to  the  advent  of  the 
"talking  picture."  It  is  not  to  be  inferred  that  these  two  men  were 
the  first  to  think  of  ''talking  pictures"  with  the  sound  recorded  on  the 
film,  but  credit  is  due  them  for  their  efforts  in  accomplishing  and  pre- 
senting for  commercial  development  what  had  heretofore  been  ac- 
complished only  in  the  laboratory  or  had  been  conceived  but  never 

The  pallophotophone  and  its  uses  and  demonstrations  aroused  at- 
tention to  a  requirement  that  had  been  of  considerable  importance  to 
the  record  industry  previously  to  this  time;  namely,  the  constancy  of 
speed  that  should  be  maintained  in  recording  as  well  as  in  reproducing 
sound  on  film. 

It  was  found  that  when  recording  sound  on  a  continuous  strip 
of  film,  particularly  the  recording  and  reproducing  of  sustained 
notes,  the  least  possible  variation  of  speed  of  the  film  was  required 
as  it  moved  past  the  recording  or  the  reproducing  light.  These 
variations  would  produce  objectionable  variations  in  the  reproduced 
sound  and  prevent  it  from  being  a  faithful  replica  of  the  original 
sound.  It  was  apparent,  then,  that  with  the  advent  of  the  talking 
picture,  suitable  equipment  for  recording  sound  on  film  and  for  re- 
producing the  sound  from  the  film  would  be  required.  Mr.  Hoxie 
and  some  of  his  associates  designed  and  built  a  film  recorder  known 
at  the  time  as  the  kinegraphone,  later  known  as  the  photophone  film 
recorder.  This  device,  designated  the  PR-1  Recorder,  employed  a 

*  The  name  pallophotophone  has  been  given  to  devices  used  for  permanently 
recording  speech  as  a  wavy  trace  on  a  moving  photographic  film,  and  for  trans- 
forming the  air  vibrations  of  sound  directly  into  exactly  corresponding  electrical 
vibrations  for  transmission;  for  example,  to  wireless  broadcasting  generators. 
The  word  is  a  Greek  derivative,  signifying  "dancing  light." 

214  A.  G.  ZIMMERMAN  [j.  S.  M.  P.  E. 

synchronous  motor  and  a  train  of  gears  driving  two  sprockets.  As 
the  film  passed  through  the  recorder,  it  was  drawn  over  a  cylindrical 
drum,  to  which  a  flywheel  was  attached  by  means  of  a  shaft.  This 
drum  was  isolated  from  the  sprockets,  and  the  sprocket-tooth  pulsa- 
tions, by  means  of  loops  of  film  threaded  around  suitable  rollers, 
although  the  film  was  relied  upon  to  drive  the  drum.  Acoustical 
power  recording  methods  could  no  longer  be  used;  the  method  of 
recording  on  the  film,  in  the  PR-1  recorder,  was  an  outgrowth  of 
Hoxie's  work  with  the  telegraphic  recorder  and  other  work  done  in 
the  laboratories  of  the  General  Electric  Company  on  oscillographs 
and  vibrators.  In  the  field,  the  PR-1  recorder  performed  remarkably 
well,  notwithstanding  the  obstacles  with  which  it  had  to  cope.  It 
was  the  first  commercial  film  recorder  to  be  called  upon  to  withstand 
the  rebuffs  of  a  slightly  unsympathetic  film  industry,  to  say  nothing 
of  some  rather  belligerent  directors  and  directors'  staffs.  A  new  era 
had  dawned  in  the  film  world,  and  the  PR-1  took  its  place  in  the  front 
ranks  of  the  invaders. 

Recollections  are  not  all  that  remain  of  the  hectic  days  during  the 
nascency  of  "sound"  and  its  adoption  by  the  already  mature  and  un- 
doubtedly independent  silent  film  industry.  Much  was  to  be  learned 
from  the  conditions  prevailing  in  the  studios  under  which  the  sound 
equipment  would  have  to  work.  Where  laboratory  experiments  had 
sufficed  for  the  original  developments,  field  experience  was  now  to  be 
had;  and  in  so  far  as  the  recorder  was  concerned,  commercial  film  pre- 
sented problems,  both  chemical  and  mechanical.  Only  the  me- 
chanical difficulty  of  shrinkage  and  its  relation  to  the  attainment  of 
constant  speed  will  be  discussed.  In  the  PR-1  recorder,  the  isolating 
loops  between  the  sprocket  and  the  film  drum  were  of  such  a  nature 
that  when  a  disturbance  occurred  in  the  speed  of  the  film  during  re- 
cording, more  filtering  or  damping  action  was  required  than  the 
flywheel  alone  would  furnish.  This  resulted  in  an  unsteady  motion 
of  the  film  past  the  recording  light  beam. 

A  new  recorder,  the  PR-3,  was  developed,  in  which  was  employed 
a  mechanical  device  to  compensate  for  the  shrinkage  of  the  film. 
In  the  PR-3,  a  synchronous  motor  was  used  to  drive  a  flywheel 
through  a  pinion  and  gear,  or  a  worm  gear  reduction.  On  the  same 
shaft  with  the  flywheel,  within  the  recorder  head,  a  sprocket  was 
mounted,  which  pulled  the  film  from  the  film  magazine.  A  cone  on 
this  shaft  was  arranged  to  drive  another  cone  on  the  recording  drum 
shaft  through  the  medium  of  an  idler,  the  position  of  which  was 

Mar.,  1933] 



determined  and  controlled  by  means  of  a  compensating  roller  in  the 
film  path  within  the  recorder  head.  This  mechanism  would  compen- 
sate for  shrinkage  of  the  film,  causing  the  speed  of  the  recording  drum 
to  be  in  accordance  with  the  exact  linear  dimension  of  the  film.  This 
compensating  mechanism,  although  a  mechanical  device,  served  to 
make  sound-film  very  superior  to  that  obtainable  with  the  now  ob- 
solete PR-1  recorder. 

As  was  to  be  expected,  the  device  employing  the  mechanical  means 

cLTt    | 


FIG.  1.     Speed-torque  curve  of  the  electromag- 
netic drive  of  the  PR  recorder. 

of  maintaining  a  constant  film  speed  in  the  PR-3  recorder  was  not 
free  from  mechanical  troubles,  starting  with  the  friction  between  the 
cone  and  the  idler  of  the  compensating  mechanism.  Mr.  E.  W. 
Kellogg,  of  the  General  Electric  Research  Laboratories,  realizing 
the  difficulties  of  the  mechanical  compensating  device,  and  aware 
of  the  advantages  to  be  gained  by  isolating  the  film  drum  from  the 
remainder  of  the  operating  mechanism,  developed  in  the  laboratory  a 
recorder  that  employed  a  magnetically  overdriven  drum.1  The  ad- 
vantages of  this  construction  were  immediately  apparent,  and  a  new 
type  of  recorder  was  designed  and  built,  in  which  were  incorporated  all 
the  advantages  of  the  earlier  recorders  as  well  as  the  improvements 
necessary  to  overcome  the  disadvantages  or  troubles  encountered  in 

216  A.  G.  ZIMMERMAN  [j.  S.  M.  P.  E. 

manufacturing  them  and  operating  them  in  the  field.  This  recorder 
was  known  to  the  industry  as  the  PR-4.  With  this  instrument  it  was 
feasible  to  record  on  film  the  sustained  notes  of  the  piano,  without 
being  able  to  detect  any  variation  of  frequency  when  the  sounds  re- 
corded on  the  film  were  reproduced.  Having  accomplished  this  ob- 
jective of  maintaining  a  sufficiently  constant  speed  of  the  film,  it  then 
became  necessary  to  combine  the  new  features  that  enabled  this  to  be 

FE£D    MAQA.7.1NE 


FIG.  2.     Front  view  of  a  model  4PR18A1  35-mm.  film  recorder  showing 


done  with  other  features  that  were  the  outgrowth  of  extensive  field  ex- 

With  the  development  and  manufacture  of  the  PR-4  recorder,  the 
limitations  and  other  objectionable  features  of  the  oscillographic  type 
of  galvanometer  were  vacated  by  using  a  galvanometer  of  such  design 
that  the  moving  parts  were  more  readily  controllable  and  the  fre- 
quency range  extended  beyond  what  was  reasonably  and  economically 
possible  with  the  oscillographic  type  of  vibrator.  After  a  recorder 

Mar.,  1933] 



embodying  this  new  vibrator  had  been  placed  in  service  in  the  field, 
the  advantages  of  reducing  the  ground  noise  of  the  film  record,  dur- 
ing passages  of  small  amplitude  or  during  quiet  intervals,  became 
apparent.  This  consideration  led  to  the  development  of  equipment 
comprising  an  amplifier  arranged  to  operate  a  shutter  vane,  which 
intercepted  part  of  the  beam  of  the  recording  lamp,  so  that,  when  the 
amplitude  of  the  sound  that  was  being  recorded  exceeded  a  certain 
threshold  level,  the  full  output  of  the  amplifier  would  be  available. 
This  arrangement  improved  the  quality  of  the  record  considerably, 



PAD  V. 


FIG.  3.     Front  view  of  type  PR-19  16-mm.  film  recorder  showing  threading. 

as,  by  means  of  it,  shots  taken  without  speech  or  music  would  be 
almost  completely  "blacked  out"  on  the  positive  film  and  neither 
scratches  nor  dust  would  cause  disturbances  in  the  reproduced 

By  the  time  the  PR-4  recorder  was  operating  in  the  field,  the  public 
had  whole-heartedly  accepted  the  talking  picture,  so  that  in  that 
respect  the  metamorphosis  of  the  silent  picture  was  complete.  Di- 
rectors and  associates,  including  the  actors,  had  come  to  realize  that 
the  technic  of  recording  sounds  on  film  had  changed  the  old  order  of 



[J.  S.  M.  P.  E. 

affairs  to  such  an  extent  that,  with  complete  cooperation,  the  art 
was  considerably  advanced. 

In  order  to  keep  pace  with  the  rapid  advances  made  in  the  labora- 
tories and  in  the  field,  where  literally  thousands  of  technical  men  were 
developing  new  equipment  or  operating  the  old  equipment  (on  a  com- 
mercial basis),  it  was  necessary  to  provide  the  film  industry  with  new 
and  improved  tools.  Consider  by  what  yardstick  the  new  recorders 
were  to  be  measured:  primarily,  as  has  been  shown,  the  recorder 

O   TVPt    PfV79  P 

FIG.  4.     Front  view  of  a  model  4PB36A1  35-mm.  film  phonograph. 

would  be  required  to  record  sound  on  film  with  the  utmost  attainable 
as  regards  constancy  of  speed  and  range  of  frequency.  The  recorder 
would  have  to  embody,  as  well,  the  attributes  of  ruggedness,  sim- 
plicity, flexibility,  and  durability.  High  fidelity  was,  then,  to  be 
realized,  at  least  as  far  as  recording  was  concerned,  in  the  latest  film 
recorder  available  to  the  film  world — the  PR-18, 

From  the  point  of  view  of  the  recorder,  we  find  high  fidelity  re- 
quiring two  important  features,  as  before:     constancy  of  speed  and 

Mar.,  1933] 



adequate  range  of  frequency.  In  so  far  as  the  speed  was  concerned, 
with  the  electromagnestically  driven  recorder  drum  as  used  in  the 
PR-4,  constant  frequency  recordings  of  continuous  frequencies  were 
assured,  without  perceptible  variations  of  speed.  (It  is  to  be  noted 
that  in  making  measurements  of  this  kind,  the  methods  used  are 
rather  simple  but  the  work  becomes  quite  fine  and  would  warrant 
a  detailed  description  not  possible  at  this  time.)  A  sleeve-bearing 
formed  the  journal  for  the  sound-drum  shaft,  so  it  was  necessary  to 


\\  „. (..ftfnP  ADJUSTMENT  CS.RMP 

T    ROTATIONAL   RSuUSTMEBT-,  \\  \  \    r<ju«y> 



\         .  SWITCH 

KcMn  etcoKope 


FIG.  5.     Front  view  of  type  PB-38  35-mm.  to  16-mm.  film  re-recorder  showing 


develop  a  combination  of  bearing  and  shaft  metals  and  a  lubricant 
that  would  insure  minimum  friction,  minimum  bearing  noise  (me- 
chanical), and  maximum  uninterrupted  service.  The  shaft  and 
sound-drum  of  the  recorder  were  made  of  stainless  steel  so  as  to  avoid 
corrosion.  Considerable  developmental  work  had  to  be  done  before 
the  proper  combinations  were  determined  and  acceptably  proved. 
From  the  electrical  point  of  view,  although  the  magnetic  drive  has 
been  explained  previously, 1  a  brief  description  of  it  may  be  in  order  at 
this  point.  It  consists  of  a  solid  copper  annulus,  fixed  in  a  support- 



[J.  S.  M.  P.  E. 

ing  flywheel  attached  to  the  drum-shaft.  An  electromagnet,  driven 
by  the  recorder  motor  through  reduction  gears,  is  constructed  so  that 
an  annular  air-gap  is  formed  on  its  rear  surface.  The  copper  ring, 
by  reason  of  its  construction,  fits  into  the  air-gap  and  rotates  only 
when  the  electromagnet  is  properly  excited  by  a  direct-current  source. 
Fig.  1  shows  a  speed-torque  curve  of  the  magnetic  drive  motor. 
In  this  curve,  NIi  represents  the  field  excitation  for  a  given  current; 
and  TV/2  the  excitation  for  a  greater  current,  producing  a  proportion- 
ately greater  flux  density  in  the  air-gap.  From  this  figure,  it  is  evi- 

FIG.  6. 

Front  view  of  a  4PB38A1  35-mm.  to  16-mm.  re-recorder  showing 

dent  that  for  small  changes  of  speed  (dS)  of  the  film  drum  (no  matter 
what  the  cause),  there  will  be  an  opposing  or  damping  action  mea- 
sured as  an  increment  of  torque  in  accordance  with  the  subtended  lines 
shown  on  the  vertical  scale.  It  is  further  evident  that  the  greater 
the  slope  of  the  curve,  the  greater  will  be  the  damping  produced  by 
the  increment  of  torque  dT.  The  magnet  drive  in  the  recorder  is 
usually  designed  to  drive  the  magnets  at  a  speed  that  is  approximately 
10  per  cent  greater  than  the  speed  of  the  drum. 

An  optical  system2  capable  of  responding  faithfully  to  the  in- 
creased frequency  range,  and  yet  simple  and  rugged  enough  to  be  a 

Mar.,  1933]  FILM  RECORDERS  221 

practical  "tool,"  had  to  be  designed.  The  optical  parts  in  general 
were  mounted  on  a  unit  casting  and  designed  so  as  to  prevent  all 
possible  variations  in  their  arrangement.  The  galvanometer  was  of 
a  new  type,  necessitated  by  the  extension  of  the  range  of  frequency  of 
the  response.  It  is  of  the  balanced  armature  type,  and  employs  a 
mirror  of  such  dimensions  that  the  "edge  to  area"  ratio  is  reduced  to 
a  harmless  minimum,  resulting  in  a  substantial  reduction  of  the  stray 
light  impinging  on  the  film.  The  stray  light  is  reduced  still  further 
by  mounting  the  window  in  front  of  the  mirror  at  an  angle,  so  that 
any  secondary  reflection  from  it  will  not  impinge  upon  the  mechani- 
cal slit.  The  reduction  of  the  stray  light  and  the  increase  in  the 
area  of  the  mirror  permit  the  use  of  a  less  sensitive  film  for  a  given 
current  in  the  exposure  lamp. 

The  operation  of  the  optical  system  differs  from  that  of  all  previous 
types  in  that  the  sound  track  is  recorded  by  moving  a  triangular  light 
image  in  a  vertical  direction  across  a  horizontal  slit,  and  optically 
reducing  the  cross-section  of  the  light  beam  so  that  the  sound  track 
becomes  a  serrated  pattern  on  the  film,  varying  from  a  0.002-inch  line 
at  the  center  to  the  full  width  of  the  sound  track,  on  both  sides  of  the 
center.  The  resulting  sound  negative  then  becomes  two  identical 
serrated  transparent  areas,  completely  separated  by  an  opaque  area. 
One  description  given  of  the  sound  track  is  that  it  resembles  "a 
mountain  chain  and  its  reflection,  as  mirrored  in  a  body  of  water  at 
the  foot  of  a  range." 

In  this  optical  system,  the  ground  noise  is  reduced  by  depressing 
the  light  image  (by  direct  current  supplied  by  the  ground  noise 
reduction  amplifier)  to  such  an  extent  that  the  tip  of  the  triangular 
light  image  is  just  incident  upon  the  mechanical  slit.  This,  produces 
on  the  film  an  opaque  track  0.002  inch  wide.  By  means  of  a  bias 
winding  in  the  galvanometer,  in  addition  to  the  modulation  winding, 
and  by  using  the  ground  noise  reduction  amplifier,  this  depressing  ac- 
tion is  made  to  occur  when  no  modulation  is  present  in  the  recording 
channel.  As  soon  as  modulation  occurs,  or  a  modulating  signal  is 
picked  up  by  the  microphone,  the  ground  noise  reduction  amplifier, 
by  means  of  a  timed  circuit,  operates  and  permits  the  modulation 
coil  of  the  galvanometer  to  vibrate  the  mirror  in  accordance  with  the 
incoming  alternating-current  signal.  The  mechanical  construction 
of  the  galvanometer  is  extremely  simple,  and,  due  to  the  fact  that  the 
armature  is  designed  so  as  to  become  saturated  at  a  predetermined 
flux  density,  the  galvanometer  is  practically  self-protecting. 

222  A.  G.  ZIMMERMAN  [j.  S.  M.  P.  E. 

A  volume  level  indicator  or  "monitor"  is  mounted  on  the  top  rear 
surface  of  the  base  casting.  It  consists  primarily  of  a  small  paper 
screen  upon  which  a  small  portion  of  the  vibrating  light  beam  is 
focused.  This  small  portion  of  the  beam  is  reflected  to  the  screen, 
through  a  window  in  the  cover,  by  a  mirror  that  intercepts  an  inde- 
pendent beam  of  light  parallel  to  the  recording  beam.  By  drawing 
lines  on  the  card  and  by  observing  the  relative  position  of  the  light 
beam  while  recording,  it  is  possible  to  observe  very  accurately  the 
modulation  of  the  sound  track. 


FIG.  7.  .  Optical  system  used  in  type  PR- 18  film  recorders.     Top  view  with 

cover  removed. 

Having  the  elements  of  a  successful  recorder,  namely,  the  constant- 
speed  film  drive  and  the  optical  system,  it  was  then  necessary  to  in- 
sure mechanical  reliability  by  mounting  all  the  equipment  on  a  rugged 
base.  This  base  was  designed  to  house  and  protect  all  the  apparatus 
incident  to  the  recorder  itself,  such  as  the  galvanometer  transformer, 
the  lamp  control  rheostat,  and  the  field  rheostat.  Connections  were 
made  to  the  audio  and  power  circuits  of  the  recorder  by  means  of 
Twist-Loc  receptacles  mounted  in  panels  on  the  rear  of  the  base. 
This  method  of  connection  avoids  permanent  wiring  of  the  installa- 
tion. Provision  was  then  made  for  a  control  panel,  whereon  the  lamp 

Mar.,  1933] 



and  field  ammeters,  the  galvanometer,  motor,  and  the  battery 
switches  were  mounted. 

Thirty-five-mm.  recorders  of  the  PR-18  type  have  been  in  constant 
service  for  the  past  seven  or  eight  months,  and  sound  records  are  being 
commercially  produced  with  them  of  an  excellence  that  heretofore 
has  been  sought  after,  but  never  attained. 

Having  produced  such  a  recorder,  embodying  all  the  mechanical 



5CCEW-    SET  IN   TH)5 




FIG.  8.     Focusing  microscope  for  use  with  35-mm.  film  recorders  and 
film  phonographs. 

features  that  have  been  mentioned,  and  having  available  all  of  the 
attributes  necessary  to  record  sound  on  film  at  a  constant  speed,  it 
was  immediately  evident  that  these  features  could  be  incorporated 
into  an  equipment  capable  of  reproducing  sound  with  the  same 
nicety.  In  order  to  accomplish  this,  it  was  necessary  to  replace  the 
optical  system  of  the  recorder  with  a  system  designed  to  reproduce 
the  high  fidelity  records  made  with  the  recorder.  Here  again,  the 

224  A.  G.  ZIMMERMAN  [j.  s.  M.  P.  E. 

requirements  of  the  field  demanded  that  such  a  system  be  provided 
as  would  reproduce  sound  tracks  faithfully  no  matter  what  type  of 
record  was  used  or  to  what  extent  the  recordist  had  misplaced  the 
sound  track  or  misaligned  the  recording  slit.  The  optical  system  that 
was  developed  includes  a  high-intensity  filament  lamp  and  a  mechani- 
cal slit  0.0025  inch  wide,  the  latter  being  optically  reduced  to  a  slit 
dimension  at  the  film  of  0.0005  inch.  The  optical  system  is  arranged 
so  that  it  can  be  adjusted  to  the  point  of  critical  focus  by  means  of 
the  focusing  microscope.  An  important  feature  of  the  system  is  the 
arrangement  by  which  the  entire  optical  barrel  is  positively  rotated 
±2.5  degrees  in  steps  of  0.1  degree.  This  feature  enables  the  opera- 
tor to  reproduce  sound  tracks  that  have  been  made  either  in  haste 
or  when  insufficient  care  was  taken  in  aligning  the  optical  system 

FIG.  9.     Focusing  microscope — component  parts. 

slit  of  the  recorder.  This  device  has  found  considerable  favor  in  the 
field  due  to  the  facility  it  provides  for  making  the  optical  adjust- 
ments. In  speaking  of  the  focusing  microscope,  the  question  may 
arise  as  to  how  it  is  possible  to  design  a  device  of  this  type  that  can 
be  made  readily  available  for  use  in  a  recorder  as  well  as  in  a  film 
phonograph.  Fig.  8  shows  the  assembly  of  the  focusing  microscope ; 
Fig.  9  shows  the  component  parts,  indicating  the  stop  adjustment, 
which  is  set  by  the  operator  for  the  machine  with  which  he  is  using 
the  instrument. 

With  the  film  phonograph  shown  in  Fig.  4,  it  can  be  seen  that  film 
in  rolls  (kept  in  this  manner  to  prevent  reel  marks)  can  be  readily 
inserted  into  the  new  type  of  magazine  and  threaded  through  the  re- 
corder head  up  into  the  take-up  side  of  the  magazine.  The  reproduc- 
ing optical  system  is  arranged  so  that  the  light  passes  through  the 
film  to  a  photocell  mounted  in  the  door  of  the  film  phonograph.  This 
is  connected  by  means  of  a  cable  to  the  phototube  amplifier.  The 
output  of  this  amplifier  matches  the  input  of  the  microphone  distribu- 

Mar.,  1933]  FILM  RECORDERS  225 

tion  panel  of  the  standard  recording  channel.  From  here,  the  sound 
may  be  mixed  with  the  output  of  separate  microphones  or  with  the 
output  of  other  film  phonographs  in  order  to  create  various  sound 
effects  on  the  final  films. 

With  a  processed  film  reproduced  by  the  film  phonograph,  it  is 
possible  to  combine  two  or  more  sound  tracks,  to  add  sound  effects  to 
an  original  recording,  or  to  match  sound  levels  in  the  finally  edited 
picture.  The  user  of  the  equipment  is  then  enabled  to  make  high 
quality  re-recordings  and  dubbings  with  complete  confidence. 

Film  phonographs  are  usually  furnished  with  a  Selsyn  motor 
mounted  on  the  base.  They  are  used  mostly  in  re-recording  channels, 
where  the  projectors  and  recorders  are  operated  from  a  master  Selsyn 
motor-generator  set.  The  film  phonograph  is  provided  with  a  syn- 
chronous motor  drive  for  recording  incidental  sound  effects  or  for 
reproducing  "takes"  independently  in  order  to  check  the  quality  of 
recording  that  has  been  obtained. 

A  distinct  advantage  of  the  film  phonograph  as  thus  designed  is 
that  fresh  or  "green"  film,  or  rushes,  may  be  run  through  the  machine 
without  danger  of  damaging  the  emulsion  by  pulling  the  film  through 
a  sound  gate  and  shoe,  because  during  the  course  of  the  film  through 
the  film  phonograph  head  it  comes  into  contact  with  the  surface  of 
only  one  roller  immediately  before  it  enters  upon  the  sound  drum. 

This  device,  like  the  recorder,  is  equipped  to  accept  all  power 
and  sound  circuits  in  suitable  Twist-Loc  connectors  mounted  on  panels 
on  the  rear  of  the  film  phonograph  base.  Also,  as  in  the  recorder, 
the  controls  are  mounted  on  a  sloping  panel  directly  in  front  of  the 
operator.  The  exciter  lamp  rheostat  is  located  on  the  left-hand  side 
of  the  base  casting  within  easy  reach. 

Due  to  the  demand  for  a  recorder  capable  of  recording  sound  on 
16-mm.  safety  stock  with  a  constancy  of  speed  comparable  with  that 
obtained  with  nitrate  stock  at  90  feet  per  minute,  it  was  evident  that 
the  electromagnetic  drive  could  be  applied  to  such  a  recorder.  With 
the  idea  in  mind  that  the  greatest  number  of  recordings  on  16-mm. 
film  would  be  made  by  direct  re-recording,  the  recorder  was  built  as 
the  reverse  of  the  35-mm.  film  phonograph.  This  was  done  so  that 
both  machines  could  be  mounted  on  a  single  base,  to  be  driven  by 
one  motor  and  the  controls  and  necessary  optical  systems  brought 
within  easy  reach  and  observation  of  the  operator.  The  16-mm. 
recorder,  although  operating  at  only  36  feet  per  minute  and  handling 
safety  stock  with  its  inherent  difficulties,  embodies  the  same  features 

226  A.  G.  ZIMMERMAN  [j.  s.  M.  p.  E. 

that  are  found  in  the  35-mm.  recorder;  and  in  so  far  as  constancy  of 
speed  is  concerned,  it  has  not  been  excelled. 

In  the  development  of  the  16-mm.  recorder,  and  in  order  to  utilize 
the  advantages  of  the  magnetic  drive,  the  size  of  the  recording  drum 
had  to  be  such  that  it  was  impossible  to  use  a  device  similar  to  the 
focusing  microscope  as  used  in  the  recorder  and  the  film  phono- 
graph. A  microscope  was  therefore  mounted  in  the  side  of  the  lens 
barrel  of  the  optical  system;  arranged  so  that  it  could  be  used  to 
observe  the  emulsion  on  the  film  through  the  objective  lens  of  the 
optical  system,  and  obtain  thereby  extremely  accurate  adjustment. 
The  optical  system  includes  essentially  the  same  components,  and  the 
same  arrangement  of  these  components,  as  a  35-mm.  recording  optical 
system;  and  monitoring  is  accomplished  in  the  same  manner  as  in 
35-mm.  recording,  by  observing  the  monitoring  light  beam  as  focused 
on  the  monitor  screen  mounted  on  the  rear  of  the  casting. 

Having  available  the  high-quality  film  phonograph  and  the  16-mm. 
recorder,  it  was  thought  advisable  to  make  available,  for  those  inter- 
ested in  the  development  of  the  16-mm.  sound  library,  a  re-recorder 
capable  of  either  (a)  re-recording  from  a  35-mm.  sound  print  to  a 
16-mm.  film;  (b)  reproducing  35-mm.  sound  film  for  listening  or  dub- 
bing work;  or  (c)  recording  directly  on  16-mm.  film.  It  was  not 
thought  economical  to  make  the  original  recordings  on  16-mm.  film, 
due  to  the  fact  that  the  cost  of  cutting  and  editing  this  film,  compared 
with  that  of  making  direct  re-recordings  from  existing  35-mm.  libra- 
ries, would  be  excessive. 

The  sprockets  of  the  reproducer  and  the  recorder  are  driven  through 
reduction  gears  by  a  single  synchronous  motor,  thus  insuring  the 
synchronization  of  the  master  35-mm.  print  with  the  16-mm.  print, 
so  that  when  the  picture  is  printed  on  the  16-mm.  film  no  difficulties 
will  be  encountered  in  synchronizing  them.  The  recorder  also  in- 
cludes the  feature  of  housing  all  the  equipment  requisite  to  the  re- 
producing and  recording  mechanisms.  Controls  for  the  exciter 
lamp  and  the  exposure  lamp  are  mounted  on  either  side  of  the  casting 
near  the  front.  The  motor  switch  is  made  common  to  both  the  re- 
producer and  the  recorder  panels,  so  that  the  machine  may  be  oper- 
ated from  either  point  or  the  two  units  may  be  operated  individually. 
The  reproducer  panel  contains  the  battery  switch,  the  field  ammeter, 
and  the  exciter  lamp  ammeter.  The  recorder  control  panel  contains 
a  galvanometer  switch,  the  field  ammeter,  the  battery  ammeter,  and 
the  exposure  lamp  ammeter.  All  external  power  and  sound  circuit 

Mar.,  1933]  FlLM  RECORDERS  227 

connections  are  made  through  the  standard  Twist-Loc  terminals  in- 
serted in  panels  at  the  rear  of  the  base  casting. 

Briefly,  then,  the  35-mm.  film  recorder  has  progressed  from  a  com- 
paratively crude  device  and  utilizing  an  acoustical  method  of  modulat- 
ing the  recording  light  beam  into  a  highly  perfected  machine  in  which 
is  employed  a  drive  that  is  almost  perfect.  The  equipment  includes  an 
optical  system  approximately  half  as  large  as  the  earlier  system  and  of 
a  comparatively  simple  design.  The  recording  is  no  longer  done 
acoustically,  but  an  improved  optical  system  and  a  galvanometer  of 
rugged  construction  are  used,  capable  of  recording  faithfully  a  fre- 
quency range  from  50  cycles  to  10,000  cycles.  The  entire  equipment 
has  been  mounted  on  a  base  so  designed  that  permanent  wiring  and 
mounting  are  unnecessary,  and  all  the  controls  are  within  the  opera- 
tor's reach. 


1  KELLOGG,  E.  W.:     "A  New  Recorder  for  Variable  Area  Recording,"  /.  Soc. 
Mot.  Pict.  Eng.,  XV  (Nov.,  1930),  No.  5,  p.  653. 

2  DIMMICK,  G.  L.,  AND  BELAR,  H.:     "Extension  of  the  Frequency  Range  of 
Film  Recording  and  Reproduction,"  /.  Soc.  Mot.  Pict.  Eng.,  XIX  (Nov.,  1932), 
No.  5,  p.  401. 




Summary. — After  briefly  referring  to  the  effect  of  the  scattering  of  light  upon 
measurements  of  density,  according  to  the  way  in  which  density  is  measured,  the 
author  alludes  to  various  attempts  made  in  the  past  to  find  a  quantitative  relation 
between  the  specular  density  and  the  diffuse  density  of  a  medium.  A  special  pro- 
jection densitometer  was  designed  for  measuring  the  specular  density,  and  a  form  of 
integrating  densitometer  for  the  diffuse  density,  of  a  number  of  samples  of  negative 
and  positive  motion  picture  film.  The  results  indicate  an  exponential  relation  be- 
tween the  two  kinds  of  density,  the  time  of  development  and  the  variation  of  gamma, 
within  the  range  of  the  measurements,  being  negligible. 

The  influence  of  the  scattering  of  light  by  the  developed  silver  grain 
upon  the  effective  optical  density  of  a  photographic  deposit  is  of 
considerable  importance  to  both  practical  and  scientific  users  of 
photographic  materials.  Density,  which  is  defined  as  the  common 
logarithm  of  the  ratio  of  incident  flux  to  transmitted  flux,  instead  of 
being  a  definite  property  of  the  silver  image,  is  dependent  upon  the 
characteristics  of  the  optical  system  of  which  it  is  a  part.  If  the 
measuring  instrument  is  so  placed  as  to  record  only  the  flux  trans- 
mitted in  a  direction  normal  to  the  plane  of  a  light-scattering  medium, 
the  density  value  will  be  greater  than  for  the  case  where  the  measure- 
ment is  based  upon  the  total  transmitted  flux.  The  first  case,  which 
has  been  termed  specular  density  (d\\),  is  the  value  that  is  of  interest 
in  dealing  with  images  for  projection — lantern  slides,  motion  picture 
positives,  and  negatives  for  enlargement.  The  second  case,  which 
is  usually  spoken  of  as  diffuse  density  (d4f ),  is  of  interest  in  contact 
printing,  where  the  negative  and  the  positive  materials  are  in  juxta- 
position and  the  total  transmitted  radiation  is  effective. 

*  Communication  No.  258  from  the  Research  Laboratory  of  the  Eastman 
Kodak  Company.  Originally  published  in  /.  Opt.  Soc.  Amer.,  XII  (June,  1926), 
pp.  559-565.  In  a  subsequent  paper  by  Silberstein  and  Tuttle,  /.  Opt.  Soc. 
Amer.,  XIV  (May,  1927),  pp.  365-373,  a  formula  correlating  the  two  densities 
was  derived  from  general  theoretical  considerations. 

**  Kodak  Research  Laboratories,  Eastman  Kodak  Co.,  Rochester,  N.  Y. 



The  dependence  of  the  density  values  upon  the  manner  of  making 
the  measurement  was  the  subject  of  an  extended  controversy  be- 
tween Hurter  and  Driffield  and  Abney.1  Abney  pointed  out  the 
effect  due  to  light  scattering.  Hurter  and  DrifHeld  agreed  with  the 

FIG.  1.  Projection  densitometer:  A,  900- watt  monoplane 
filament  lamp;  B,  5-inch  condensing  lens;  X,  photographic 
material;  C,  41/2-inch  projection  lens;  D,  Martens  polarization 

criticism  offered  by  Abney,  but  stated  erroneously  that  the  scatter- 
ing interferes  only  in  plates  of  very  high  densities.  Callier,  in  his 
well  known  paper  on  the  scattering  of  light  by  photographic  ma- 
terials,2 investigated  a  number  of  photographic  emulsions,  and  con- 
cluded that  the  relation  between  diffuse  and  specular  density  was 
approximately  satisfied  by  the  equation  d\\  =  Qd-ft,  where  the  factor 

FIG.  2.  Integrating  densitometer:  A, 
250-watt  monoplane  filament  lamp;  B,  12- 
inch  integrating  sphere;  X,  photographic 
material;  D,  Martens  polarization  photom- 

Q  is  a  constant  for  a  limited  range  of  densities.  Callier 's  measure- 
ments of  diffuse  density  were  made  with  the  photographic  material 
in  contact  with  opal  glass,  which  was  assumed  to  be  perfectly  diffus- 
ing. Under  such  conditions,  the  values  he  obtained  would  be  true 

230  CLIFTON  TUTTLE  [j.  s.  M.  p.  E. 

diffuse  density  values  within  the  range  of  the  densities  measured, 
since  here  the  effect  of  interreflection  is  negligible. 

Renwick  and  Bloch3  have  shown  that  an  equation  of  the  exponen- 
tial type  fits  Callier's  data  with  greater  accuracy  than  the  linear 
function  given  by  Callier. 

It  has  been  questioned  whether  diffuse  density  measurements  give 
the  true  contact  printing  density.  Toy4  found  that  diffuse  density, 
when  measured  by  the  use  of  an  opal  diffuser,  must  be  multiplied 
by  a  constant  factor  to  give  the  true  printing  density.  Bull  and 
Cartwright,5  however,  found  that  an  integrating-sphere  densitometer 
gave  true  contact  printing  density  readings. 

The  photographic  literature  is  replete  with  discussions  of  methods 
and  instruments  for  measuring  density  and  with  treatments  of  the 
theoretical  and  practical  aspect  of  the  scattering  of  light  by  turbid 
media.  A  detailed  review  and  analysis  of  these  papers  is  beyond  the 
scope  of  the  present  work.  Those  engaged  in  photographic  research 
are  probably  aware  of  the  uncertainties  arising  from  the  use  of  differ- 
ent instruments  employing  light  sources  with  varying  degrees  of 
collimation.  On  the  other  hand,  many  scientists  who  make  constant 
use  of  the  photographic  plate  as  a  measuring  instrument  appear  to 
be  quite  unaware  of  its  limitations  in  this  respect.  The  magnitude 
of  the  difference  between  diffuse  and  specular  readings  in  the  data 
of  the  following  investigation  serve  to  emphasize  the  necessity  for 
careful  consideration  of  this  property  of  photographic  materials. 

It  is  highly  desirable  at  times  to  express  one  density  in  terms  of  the 
other,  i.  e.,  to  evaluate  contact  printing  density  from  measurements 
of  projection  density  and  vice  versa.  Such  a  case  arose  in  connection 
with  some  work  on  tone  reproduction  in  motion  pictures,  in  which 
it  was  desired  to  trace  the  reproduction  of  original  object  contrast 
through  the  steps  of  printing  the  negative  by  contact  and  projecting 
the  positive  on  a  screen.  The  measurement  of  negative  printing 
density  on  a  projection  densitometer  designed  to  measure  positive 
projection  densities  simplifies  the  problem  of  locating  corresponding 
negative  and  positive  areas,  and  eliminates  the  possible  error  that 
might  arise  from  the  use  of  two  different  instruments.  The  purpose 
of  the  work  reported  here  is  to  establish  a  relation  between  diffuse 
and  specular  density  for  certain  photographic  materials. 

The  projection  densitometer  used  was  designed  to  approximate 
the  optical  system  used  for  projecting  motion  pictures  (Fig.  1). 
Neither  the  incident  beam  nor  the  measured  component  is  strictly 

Mar.,  1933] 




Par  Speed  Motion  Picture  Negative 




d  -  calc. 


7V  r* 























—  1.4 


















































parallel.  It  is  interesting  to  note,  however,  that  the  deviation  from 
parallelism  was  so  slight  that  a  check  of  this  instrument,  m?de  with 
the  bench  photometer  using  collimated  light,  showed  no  difference 
in  density  readings. 

I"  TO 

Par  Speed  Mo+ion  Picf  ore  Nega+ive 


















1-6  Ta          o-o          o-z 

Log  Specular  DensH-y 

FIG.  3.     Curve  plotted  from  data  of  Table  I. 



[J.  S.  M.  P.  E. 


Motion  Picture  Positive 

d-H-                       d\\                    d\\/d-{\-             d-H-calc. 






L.44            0.0483 





.152              ] 

L.44            0.108 





.316              ] 

L.37            0.231 





.523              ] 

L.36             0.390 

+  1.3 




.590              ] 

L.34            0.442 





.651              ] 

L.34            0.489 






.35            0.575 

+  1-7 





.31            0.686 






.32            0.771 






.29            0.946 






.29            0.978 





.95                1.30            1.52 



A  form  of  integrating  densitometer  (Fig.  2)  was  chosen  to  make 
the  so-called  "diffuse  density"  measurements,  because  from  its  nature 
it  actually  measured  the  total  transmitted  light.  This  instrument 
makes  use  of  the  same  Martens  polarization  photometer  mounted 






Mof  ion  Picture.  Posif  luc. 













0              ~\Z               1-4-             16              T-8             0-0              0-Z 

Log  Specular  Density 

FIG.  4.     Curve  plotted  from  data  of  Table  II. 

Mar.,  1933] 




Eastman  40 




d-H-  calc. 































































in  the  same  supporting  unit  as  is  used  with  the  projection  densitome- 
ter.  The  essential  difference  between  the  two  instruments  is  in  the 
measurement  of  transmitted  flux. 

A  number  of  densities  ranging  from  0.05  to  2.00  were  prepared 
and  measured  on  both  instruments.  Tables  I,  II,  and  III  give  the 
average  of  five  readings  for  each  density.  Column  3  gives  the  ratio 



Easfman  40 

To  Tz  1-4-  1-fe  1-8  oo          o-z 

Log  Specular  Density 

FIG.  5.     Curve  plotted  from  data  of  Table  III. 

234  CLIFTON  TUTTLE  [j.  s.  M.  p.  E. 

of  specular  to  diffuse  density  —  the  Callier  Q-factor.  Evidently  a 
linear  relation  will  not  satisfy  the  data.  The  variation  of  Q  is  about 
thirty  per  cent.  The  data  seem  to  be  very  much  more  applicable  to 
an  exponential  equation,  such  as  was  suggested  by  Renwick  and 
Bloch  (loc.  cit.). 

Figs.  3,  4,  and  5  show  the  data  of  Tables  I,  II,  and  III  plotted  loga- 
rithmically. A  straight  line  represents  the  locus  of  log  d||/log  d-\\-, 
with  a  maximum  error  less  than  the  error  of  measurement. 

The  equation  of  these  curves  is  of  the  form, 

log  d-\\-  =  m  log  d  1  1  —  c 
or      J4f   =  d 

where  m  is  the  slope  and  c  the  intercept. 

The  values  of  these  constants  for  the  three  emulsions  investigated 
are  as  follows: 

m  Antilog  c 

Par  Speed  Motion  Picture  Neg.                     1  .  088  1.37 

Motion  Picture  Positive                                   1  .  036  1.31 

Eastman  40                                                       1.091  1.30 

The  values  of  d-\\-  as  calculated  from  d\\  by  the  formula  are  given 
in  column  4  (Tables  I,  II,  and  III),  and  the  difference  of  percentage 
(e)  between  the  observed  and  calculated  values  in  column  5. 

A  number  of  samples  of  motion  picture  negative  emulsion  were 
developed  for  different  times,  the  gamma  (the  slope  of  the  Hurter 
and  Driffield  characteristic  curve)  being  varied  from  0.4  to  1.0  in 
order  to  determine  the  effect  of  the  development  upon  the  ratio  of 
the  specular  to  the  diffuse  density.  It  was  concluded  that  the  effect 
within  this  range  was  negligible.  Three  sets  of  motion  picture  nega- 
tive densities  representing  three  different  batches  of  the  same  kind 
of  emulsion  were  tested,  and  the  results  were  in  very  good  agreement. 
It  is  doubtful,  however,  whether  the  constants  m  and  c  will  hold 
with  equal  accuracy  for  all  batches  of  the  same  emulsion,  since  the 
average  grain  size  differs  slightly  from  batch  to  batch. 

In  column  5  of  Tables  I,  II,  and  III  is  given  the  ratio  of  the 
scattered  transmitted  light  to  the  total  transmitted  light  as  deter- 
mined from  the  density  values.  The  increase  of  this  ratio  is  prac- 
tically constant  with  respect  to  decreasing  transmission  values  from 
100  to  30  per  cent. 

The  relation  of  the  scatter  ratio  to  the  density  is  not  linear  even 
for  low  values  of  density,  as  was  observed  by  Eggert  and  Archenhold,6 


and  therefore  is  not  linearly  proportional  to  the  mass  of  the  scattering 
material  present.  It  is  possible  that  the  scatter  ratio  may  be  some 
function  of  the  perimeter  of  the  interstices  between  the  silver  particles, 
and  it  is  hoped  that  by  the  use  of  single  grain  layers,  some  such  cor- 
relation may  be  found. 


1  HURTER,  F.,  AND  DRiFFiELD,  V.  C.i     "Photo- Chemical  Investigations  and 
a  New  Method  of  Determination  of  the  Sensitiveness  of  Photographic  Plates," 
J.  Soc.  Chem.  Industry  (May,  1890),  p.  455. 

ABNEY,  W.  M.  W.:  "On  the  Accuracy  of  the  Grease  Spot  Photometer  for 
Measuring  the  Density  of  Photographic  Plates  and  a  Note  on  the  Sector  Photom- 
eter," /.  Soc.  Chem.  Industry  (July,  1890),  p.  722. 

HURTER,  F.,  AND  DRIFFIELD,  V.  C.:  "Reply  to  the  Preceding  Communi- 
cation of  Captain  Abney,"  etc.,  J.  Soc.  Chem.  Industry  (July,  1890),  p.  725. 

2  CALLIER,    A.:     "The   Absorption   and   Scatter   of   Light   by   Photographic 
Negatives,    Measured   by   Means   of   the   Martens    Polarisation   Photometer," 
Phot.  J.,  49  (1909),  p.  200. 

3  BLOCK,   O.,   AND   RENWICK,   F.    F.:     "The   Opacity  of   Diffusing  Media," 
Phot.  J.,  40  (1916),  p.  49. 

4  BULL,  A.  J.,  AND  CARTWRIGHT,  H.  M.:     "An  Evaluation  of  the  Light  Scat- 
tered by  Photographic  Densities,"  Phot.  /.,  49  (1925),  pp.  125,  177. 

5  CARTWRIGHT,    H.    W.:     "The    Measurement    of    Photographic    Density," 
Phot.  J.,  48  (1924),  p.  180. 

6  EGGERT,  J.,  AND  ARCHENHOLD,  G.:     "Das  optische  Streiwermogen  photo- 
graphisch  entwickelter  Silberschiehten,"  Zeit.  fur  Physik  Chemis,   110  (1924), 
p.  497. 


Summary. — The  paper  describes  methods  of  using  sheet  film  base  in  making 
models  for  experimental  processes.  Methods  of  cutting  and  scraping  the  material 
are  described  at  length,  as  also  the  manner  of  making  and  using  the  requisite  thick 
and  thin  cements  employed  in  making  welds.  Various  illustrations  are  given  in 
order  to  exemplify  the  processes. 

Experimenters  in  the  time  of  Newton  or  Priestley  were  proud  to 
boast  that,  from  a  jam  jar,  some  string,  and  a  piece  of  sealing  wax, 
they  could  construct  most  of  their  physical  apparatus. 

Nowadays,  although  our  laboratories  are  supplied  with  a  variety  of 
intricate  devices  and  pieces  of  glassware,  many  problems  demand 
the  construction  of  special  apparatus.  The  methods  at  our  disposal 
vary  with  our  constructive  skill,  but  rarely  embrace  more  than 
carpentering,  glass  blowing,  soldering  and  sheet  metal  working, 
plumbing,  and  elementary  electric  wiring. 

Of  these,  with  the  advent  of  Pyrex,  it  may  be  said  that  glass  work- 
ing is  probably  the  most  useful,  and  the  least  dispensable.  To  be 
able  to  see  what  is  happening  inside  the  apparatus  is  the  great  ad- 
vantage, outweighing  a  hundred  minor  drawbacks.  If  metal  working 
could  produce  transparent  articles,  the  value  of  soldering  and  plumb- 
ing would  be  greatly  enhanced,  and  many  experimental  problems 
would  be  simplified.  This  article  does  not  describe  such  a  miracle, 
but  it  does  compromise  by  showing  how  transparent  cellulose  com- 
pounds may  be  built  into  useful  laboratory  apparatus. 

Transparent  cellulosic  sheeting  is  generally  made  from  cellulose 
nitrate  or  cellulose  acetate.  The  more  usual  nitrate  material  is 
commonly  known  as  celluloid.  Since,  however,  this  is  a  trade  name 
for  a  special  product,  we  shall  speak  of  the  material  as  nitrate  base 
or  sheet;  and  refer  to  cellulose  acetate  sheeting  as  acetate  base. 

A  word  as  to  the  properties  of  these  two  substances:     nitrate  sheet 

*  Communication  No.  370  from  the  Kodak  Research  Laboratories.     Revised 
from  the  original  article  published  in  /.  Franklin  Institute,  207  (Feb.,  1929), 
pp.  231-244. 


is  a  mixture  of  cellulose  nitrates  plasticized  with  camphor.  It  is 
not  only  inflammable,  but  it  also  decomposes  in  the  absence  of  air. 
Decomposition  begins  between  140°  and  170°C.,  and  ignition 
occurs  at  a  higher  temperature.  Below  the  boiling  point  of  water  it 
softens  sufficiently  for  molding. 

Acetate  base,  on  the  other  hand,  since  it  contains  no  camphor, 
is  not  so  plastic  or  easily  molded.  It  can  be  bent  at  a  temperature 
of  100  °C.,  and  will  retain  its  new  shape  when  thus  bent.  It  does  not 
decompose  spontaneously  in  the  absence  of  air  at  temperatures  be- 
low its  ignition  point,  and  it  does  not  burn  with  special  vigor.  Hence 
its  use  for  safety  cinematograph  film  and  home  motion  pictures. 
Both  materials  are  softened  by  certain  organic  solvents,  and  two 
pieces  may  be  stuck  together  by  placing  a  drop  of  solvent  between 
them  and  squeezing  them  into  intimate  contact.  The  solvent  softens 
and  partially  dissolves  the  surfaces,  and  is  then  absorbed  by  the  mass 
of  the  material  as  water  is  absorbed  by  gelatin.  Later  it  evaporates. 
The  process,  however,  can  produce  a  good  autogenous  weld  of  a 
strength  nearly  equal  to  that  of  the  original  material. 

Nitrate  and  acetate  bases  may  be  bent  and  welded  into  compli- 
cated shapes.  Since  they  may  be  stuck  to  glass,  elaborate  apparatus 
may  be  built  up  of  dimensions  difficult  to  obtain  with  glass  tubes 
alone.  Examples  will  be  described  later. 

Besides  the  inability  to  resist  heat,  neither  material  will  with- 
stand strong  liquids.  The  vague  term  "strong  liquids"  may  be 
applied  to  the  following: 

Nitrate  Base  Acetate  Base 

Concentrated  nitric  acid  Moderately  concentrated  acids 

Concentrated  hydrochloric  acid  2  per  cent  alkali 

Concentrated  sulfuric  acid  Acetone 

10  per  cent  or  stronger  caustic  alkali  Alcohol 

Acetone  Ether 

Alcohol  Amyl  acetate 
Amyl  acetate 

Both  bases  will  withstand  water,  solutions  of  metallic  salts,  dilute 
acids,  carbonates,  benzene,  chloroform,  and  xylene.  Nitrate  base 
will  resist  20  per  cent  sulfuric  acid  indefinitely. 


The  operations  involved  in  working  with  nitrate  base  are  four  in 
number,  and  are  extremely  simple. 

238  K.  HICKMAN  AND  D.  E.  HYNDMAN         [J.  S.  M.  P.  E. 

They  are 

(1)  Cutting 

(2)  Shaping 

(3)  Welding: 

(a)     to  like  material, 

(6)     to  glass  and  other  substances 

(4)  Laminating 

Directions  given  below  for  nitrate  base  serve,  in  practically  every 
instance,  for  acetate  base. 

(1)  Cutting. — Nitrate  sheet  that  is  to  be  cemented  perpendicularly 
to  the  surface  of  a  second  piece  (Fig.  1)  should  never  be  cut.     The 
scissors  should  be  reserved  for  trimming  the  edges  of  finished  articles. 
No  matter  how  carefully  the  cut  is  made,  the  edge  will  deviate  slightly 
from  a  straight  line  or  pure  curve.     A  convenient  way  to  part  ni- 
trate or  acetate  sheeting  is  to  draw  a  sharp  point,  in  pencil  fashion, 
along  a  straight  edge.     A  "Moore"  glass  push-pin  works  well,  and 
may  be  discarded  when  the  point  is  blunt.     Old  razor  blades  are  not 
suitable  because  they  tend  to  depart  from  the  marked  line.     When 
a  good  clean  scratch  has  been  made,  the  material  is  bent  until, 
with  a  slight  snap,  it  parts  along  the  entire  length.     Circles  are  cut 
with  the  dividers,  placing  a  piece  of  scrap  sheet  under  the  center 
leg  so  as  to  avoid  making  a  large  pivot  hole.     Two  or  three  revolu- 
tions with  the  dividers  leaning  in  the  direction  of  travel  will  make  a 
deep  enough  scratch.     If  the  internal  circle  is  to  be  used,  two  or 
three  scratches  are  ruled  tangentially  to  the  circumference,  and  the 
outer  portion  is  broken  away.     When  it  is  the  outer  ring  that  is 
wanted,  the  inner  circle  must  be  detached  by  carefully  applying 
pressure  with  the  thumbs.     It  is  better  to  work  the  material  back- 
ward and  forward  than  to  apply  excessive  force. 

Other  shapes  are  easy  to  produce.  An  ellipse  is  made  by  guiding 
the  cutting  point  with  a  loop  of  string  held  between  two  fixed  pivots. 
Wavy  contours  are  produced  with  French  curves.  The  line  is  first 
built  up  with  a  grease  pencil  from  various  positions  of  the  curve  and 
is  then  retraced,  still  using  the  curve,  with  the  sharp  point. 

(2)  Shaping. — The  many  cellulose  nitrate  articles  available  com- 
mercially are  evidence  that  with  molds  and  dies  any  shape  can  be 
produced.     Molds  are  not  common  in  the  laboratory,  so  that  the 
shaping  operation  is  generally  limited  to  simple  bending.     Varia- 
tions of  the  cube  and  the  cylinder  are  practicable,  but  not  of  the 

Mar.,  1933]  MODEL  MAKING  WITH  FlLM  BASE  239 

Three  kinds  of  equipment  are  requisite  for  bending:  a  square 
metal  bar,  a  selection  of  metal  rods,  and  a  vessel  of  hot  water.  The 
metal  bar  is  perhaps  the  most  useful. 

The  inflammable  nature  of  nitrate  base  would  suggest  using  hollow 
bars  and  tubes  that  could  be  warmed  with  steam  from  an  electric 
kettle.  We  have  found  it  safe,  however,  to  use  a  Bunsen  burner, 
making  sure  that  the  sheeting  and  cement  are  pushed  out  of  the  way. 

The  bar  has  available  four  edges  and  four  sides.  At  least  one 
edge  should  be  rounded,  forming  part  of  a  circle  of  about  Yie-mch 
radius  (Fig.  2).  All  four  sides  may  be  at  right  angles,  or  the  bar 
may  be  a  right-angled  triangle.  In  this  case  the  other  two  angles 
should  be  rounded  as  well.  The  bar  is  used  to  supply  heat  to  the 
sheet,  and  no  matter  how  sharp  a  bend  is  desired,  there  should  be 
sufficient  bearing  surface  to  convey  the  heat. 

The  bar  is  warmed  by  waving  the  Bunsen  flame  along  its  length 
until  the  moistened  finger  just  sizzles  when  touching  the  upper 
surface.  The  flame  is  now  extinguished,  and  the  sheet  brought  into 
contact  with  the  bar.  A  line  should  previously  have  been  ruled 
with  the  grease  pencil  where  the  bend  is  to  be  made.  On  no  account 
should  a  scratch  have  been  made.  The  ends  of  the  sheet  are  grasped 
in  the  two  hands,  and  when  it  has  begun  to  yield,  the  regions  near 
the  bend  should  be  pressed  with  wood  strips,  or  smothered  tightly 
with  a  cloth.  When  the  desired  angle  has  been  attained,  the  sample 
is  removed,  taking  care  to  maintain  the  angle  until  the  material  be- 
comes cold  (Fig.  3).  The  procedure  is  similar  when  making  a  less 
sharp  bend  around  a  rod. 

Sometimes  it  is  necessary  to  produce  an  irregular  shape  to  fit  some 
special  contour.  In  Fig.  4  the  pieces  a-a'  are  similar  and  have  two 
edges  at  right  angles,  while  the  third  follows  the  special  contour; 
a  and  a'  form  the  side  pieces  to  the  angular  strip  c.  Let  us  suppose 
it  is  necessary  to  bend  b  so  that  it  may  be  cemented  in  place  to  com- 
plete the  box.  b  is  cut  to  a  strip  x/4  inch  wider  than  called  for,  and 
at  least  an  inch  longer.  Placing  the  piece  a  beside  a  bowl  of  water 
hotter  than  the  hands  can  bear,  b  is  held  with  pliers  and  immersed. 
In  a  minute  it  is  withdrawn  and  given  a  quick  pressure  with  the  hands 
at  V  (Fig.  4a),  and  allowed  to  spring  away  again.  It  will  have  taken 
a  slightly  permanent  shape.  If  it  does  not  match  the  curve  of  a 
sufficiently,  the  warming  and  pressing  are  repeated  until  a  slightly 
exaggerated  bend  is  attained.  The  curves  at  W,  X,  Y,  and  Z  now 
receive  attention,  exaggerating  each  one,  in  order,  a  little  less  than 

240  K.  HICKMAN  AND  D.  E.  HYNDMAN         [J.  S.  M.  p.  E. 

its  predecessor.  In  this  way  the  final  sample  is  found  to  have  curves 
at  the  right  places,  but  owing  to  its  recovery  in  warm  water,  each 
curve  is  a  little  less  pronounced  than  needed.  This  is  an  advantage, 
for  when  fixture  is  made  at  the  point  T  (Fig.  4a),  pressure  at  5  brings 
the  whole  strip  into  contact  with  a  and  allows  the  cementing  to  be 
accomplished  in  one  operation. 

(3)  Welding,  (a)  Autogenous:  Base  to  Base. — The  require- 
ments are  thin  cement,  and  thick  cement,  in  suitable  containers,  and 
some  hog's  hair  brushes,  in  holders  from  which  the  varnish  has  been 
scraped.  The  containers  are  easily  made  from  16-ounce  wide  necked 
bottles  supplied  with  large  corks  that  do  not  fit  too  tightly.  Through 
a  central  hole  in  each  cork  a  stout  walled  test  tube,  3/4  inch  in  diameter 
and  6  inches  long,  is  pushed  from  below.  This  is  much  better  than 
having  the  brush  itself  fixed  in  the  cork  (Fig.  5) . 

Many  formulas  for  film  cement  have  been  published,  but  since 
only  small  quantities  are  needed,  we  have  found  it  convenient  to  use 
the  ready-made  Eastman  cement  without  inquiring  into  its  composi- 
tion. This  is  the  thin  cement  referred  to  above. 

The  thick  variety  is  made  by  dissolving  scrap  base,  cut  into  strips 
an  inch  and  a  half  long  by  Vie-inch  wide,  in  the  thin  cement.  A 
spare  bottle  is  filled  one-third  full  of  the  chips  and  cement  is  poured 
in  until  the  bottle  is  more  than  half  filled.  The  mixture  is  stirred 
vigorosly  with  a  stout  glass  rod  every  ten  minutes  throughout  the 
day  and  left  to  settle  overnight.  In  the  morning  the  clear  thick 
syrup  is  decanted  into  the  container  from  a  slight  residue  of  gelatinized 
strips.  A  brush  is  selected,  placed  in  the  syrup,  and  the  cork  thrust 

It  should  be  understood  at  the  outset  that  nitrate  sheet  sticks  to 
itself  by  virtue  of  its  own  powers  of  adherence.  The  cement  is  used 
merely  to  prepare  the  surfaces.  After  these  have  momentarily  been 
flooded,  the  best  joins  are  obtained  when  the  surfaces  are  pressed 
together  tightly  enough  to  extrude  every  trace  of  unabsorbed  liquid. 
Obviously,  the  thick  cement  will  not  be  pressed  out  as  efficiently  as 
the  thin,  and  will  therefore  not  make  as  good  a  join.  The  thick 
fluid  should  therefore  be  used  for  external  reinforcement  of  the  join. 

Joins  are  of  two  kinds,  perpendicular  and  parallel,  or  end  to  face 
and  face  to  face.  The  latter  is  lamination  on  a  small  scale. 

The  parallel  join  is  very  easy  to  make.  One  sample  is  stood  at 
an  angle  on  the  other,  and  a  few  drops  of  cement  from  a  pipette  or  a 
brush  are  laid  in  position.  The  upper  sample  is  quickly  laid  down 

Mar.,  1933]  MODEL  MAKING  WITH  FlLM  BASE  241 

and  an  even  pressure  applied  all  over  with  the  flat  of  the  hand  or  a 
cloth  pad.  A  piece  of  blotting  paper  placed  underneath  will  absorb 
the  excess  cement  pressed  from  the  edges.  The  operations  are  shown 
in  Figs.  6  and  7,  while  the  finished  join  is  being  tested  in  Fig.  8. 

The  perpendicular  join  is  more  difficult  but  is  much  more  useful. 
At  its  simplest,  the  straight  edge  of  a  piece  of  base  is  pressed  tightly 
against  the  surface  of  another  piece,  while  a  little  thin  cement  is  run 
along  the  angle  at  each  side  (Fig.  9) .  The  pressure  is  maintained  for 
30  seconds  after  all  trace  of  liquid  has  disappeared,  and  the  sample 
left  undisturbed  for  an  hour.  It  is  then  held  in  an  inclined  position 
(Fig.  10),  while  a  drop  of  thin  cement  is  placed  at  the  top  of  the  angle 
on  each  side  and  allowed  to  run  down,  which  it  should  do  quickly. 
Immediately  a  big  drop  of  thick  cement  is  placed  in  the  same  posi- 
tion and  allowed  to  fall  slowly  along  each  crevice.  At  every  inch  or 
two  of  fall  it  should  be  replenished,  not  at  the  top,  but  at  the  head 
of  the  traveling  drop.  Finally  the  sample  is  put  away  to  dry  for  one 
day  on  a  level  surface,  after  which  a  section  of  the  join  should  present 
the  appearance  in  Fig.  11.  The  object  of  the  pre- wetting  with  thin 
cement  is  to  prevent  the  inclusion  of  air  bubbles. 

If  the  thick  cement  had  been  applied  to  the  corner  with  a  brush, 
it  would  have  formed  ridges  where  they  were  least  needed,  yielding 
a  finished  product  like  Fig.  12. 

The  reinforcing  cement  must  be  used  with  caution.  It  sets  after 
partially  drying  into  the  shape  of  the  join,  but  later  when  more 
solvent  has  evaporated  it  contracts  and  pulls  the  pieces  into  a  more 
acute  angle  than  was  intended.  The  reinforcing  should  always  be 
done  on  two  sides  of  the  join  and  sometimes,  if  the  appearance  of 
Fig.  13  is  to  be  avoided,  on  three.  The  properly  finished  join  is 
shown  in  Fig.  11. 

Most  perpendicular  joins  are  less  simple.  They  are  the  kind  in- 
volved when  an  end,  a  side,  or  a  partition  is  cemented  to  a  shaped 
container.  Fitting  a  circular  disk  into  the  end  of  a  cylinder  is  per- 
haps the  simplest  case.  The  disk,  cut  to  fit  tightly,  is  pushed  into 
place  and  thin  cement  is  run  all  round.  Since  there  is  no  tendency 
for  the  join  to  come  apart,  the  thick  cement  may  follow  immediately. 
A  large  globule  is  placed  in  one  crevice,  and  the  cylinder  is  rotated 
until  the  syrup  has  fallen  all  around.  The  other  side  is  then  treated. 

Fastening  the  end  into  a  rectangular  box  is  a  little  more  difficult. 
The  sides  of  the  box  may  be  completed  before  or  after  insertion  of 
the  end.  In  the  first  case,  the  end  piece  is  cut  accurately  to  size,  but 


K.  HlCKMAN  AND  D.  E.  HYNDMAN  [J.  S.  M.  P.  E. 

the  corners  are  rounded  off  more  than  would  appear  necessary.  It  is 
thrust  into  position  and  cement  applied  at  the  center  of  the  long  sides, 
holding  them  against  the  end  piece  for  at  least  a  couple  of  minutes. 
The  centers  of  the  short  sides  next  receive  treatment,  and  cement  is 
finally  brushed  all  around.  One  hour  should  elapse  before  the  ap- 
plication of  the  thick  cement. 

FIGS.  1-13,  INCLUSIVE.     Illustrating  the  manner  of  making  the  various  kinds  of 


Mar.,  1933] 



When  the  rectangular  box  is  to  be  built  around  the  end  piece, 
it  should  be  fitted  by  trial  and  error  before  any  cementing  is  done. 
The  join  is  most  conveniently  made  in  the  middle  of  a  long  side. 

FIGS.  14-21,  INCLUSIVE.     Illustrating  the  procedure  of  making  more  complicated 


244  K.  HICKMAN  AND  D.  E.  HYNDMAN        [J.  S.  M.  p.  E. 

Cementing  of  the  top  plate  is  begun  with  one-half  of  the  split  long 
side  (Fig.  14),  being  careful  that  the  plate  is  pushed  snugly  up  to 
the  corner.  After  a  few  minutes,  the  other  sides  may  be  brought  into 
position  and  secured.  Finally  the  free  half  of  the  split  side,  previously 
given  a  rebate  by  pressing  between  two  thin  metal  plates  in  a  vise 
(Fig.  14&),  is  cemented  in  place  and  a  parallel  joint  made  all  the 
way  down  The  simplest  way  of  all  of  closing  the  rectangle  is  to  stand 
it  on  a  plate  larger  than  actually  required,  run  cement  all  around 
the  crack,  and  follow  this,  within  and  without,  by  thick  cement 
(Fig.  15). 

(4)  Lamination. — Although  joining  sheet  to  glass  and  other 
materials  is  next  in  order  for  consideration,  it  will  be  convenient  first 
to  describe  lamination.  If  two  thin  sheets  be  placed  face  to  face, 
with  their  ends  between  the  rollers  of  a  horizontal  mangle  (Fig. 
16),  cement  may  be  poured  into  the  junction  and  they  may  then  be 
rolled  into  one  homogeneous  piece.  In  place  of  a  mangle  one  may  use 
a  drawing  board  and  a  gelatin  composition  roller  of  the  kind  favored 
by  printers  for  inking  up  halftone  blocks  (Fig.  17).  With  a  ten-inch 
roller  pieces  9  by  20  inches  may  be  built  up  with  ease.  One  sheet 
11  by  25  inches  is  laid  on  the  board.  A  thin  line  of  cement  drops  is 
placed  at  one  end,  and  a  second  sheet  secured  above  it  along  this 
edge.  Holding  the  upper  sheet  at  an  angle  of  45  degree,  a  liberal 
pool  of  cement  is  poured  into  the  angle,  after  which  the  roller  is 
pushed  smoothly  but  quickly  forward.  Enough  cement  must  be 
used  to  stick  the  entire  length.  It  is  convenient  to  squirt  the  liquid 
from  the  original  can. 

Laminating  is  a  messy  operation.  The  cement  exudes  from  sides 
and  end  and  is  very  likely  to  get  on  the  board  or  under  the  clean 
bottom  face  of  the  nitrate  base.  This  may  be  prevented  by  doing 
the  operation  on  blotting  paper.  It  is  important  that  the  freshly 
laminated  material  should  have  the  uncemented  side  portions  cut 
away  at  once.  It  should  be  allowed  to  hang  vertically  for  some  hours, 
because  any  bend  suffered  at  this  stage  will  impose  a  permanent 

Nitrate  base  is  readily  obtained  in  thicknesses  of  5,  10,  and  20 
thousandths  of  an  inch.  The  20-thousandths  sheet  is  the  most  use- 
ful, and  by  laminating  two  or  three  thicknesses,  a  sheet  sturdy 
enough  for  most  requirements  can  be  made. 

The  need  is  soon  encountered  for  nitrate  tubing.  Unfortunately, 
we  have  been  unable  to  obtain  this  in  lots  of  less  than  50  pounds, 

Mar.,  1933] 



and  have  been  forced  to  make  it  by  lamination,  or  else  press  glass 
tubing  in  service.  Short  lengths  can  be  made  very  simply  after  the 
manner  shown  in  Figs.  18  and  18a.  Cement  must  not  get  between 
the  pyroxylin  and  the  glass,  otherwise  the  mandrel  can  not  be  with- 

(3b)  Welding  Nitrate  Base  to  Other  Materials, — The  base  does 
not  make  good  shafts  or  bearings,  or  good  narrow  tubes.  When- 
ever moving  parts  are  involved,  or  fluids  have  to  be  conveyed  to 
containers,  glass  or  metal  spindles  or  tubes  have  to  be  affixed  to  the 

Nitrate  base  cemented  to  smooth  glass  or  metal  adheres  fairly 
well  until  one  corner  becomes  lifted.  Then  any  slight  strain  strips 

FIG.  22.     Transparent  crystal  model. 

it  away.  This  happens  particularly  easily  under  water.  Conse- 
quently the  base  and  glass  (or  metal)  have  to  be  so  shaped  that  the 
one  surrounds  the  other  completely  and  without  the  possibility  of 

Cementing  a  Glass  Tube  into  a  Nitrate  Container. — Two  methods 
have  been  used  successfully.  In  the  first,  the  glass  is  indented  in 
the  blow  pipe  flame  and  when  cold  a  chip  of  base  is  thrust  into  the 
cavity.  A  thick  tube  is  then  laminated  over  this,  wetting  the  glass 
with  much  cement.  When  the  walls  are  a  quarter  of  an  inch  thick, 
the  whole  assembly  is  cemented  to  the  side  of  the  vessel.  Fig.  19 
shows  the  procedure  in  detail. 

The  other  method  involves  an  unsymmetrical  expansion  in  the  glass 
so  as  to  make  the  grip  secure.  A  flat  uneven  bulb  is  blown,  and  a 
number  of  washers  are  cut  to  fit  its  contours,  the  outer  ones  just 

246  K.  HICKMAN  AND  D.  E.  HYNDMAN         [j.  S.  M.  P.  E. 

fitting  the  undistorted  tube.  These  are  cemented  in  position  one 
by  one,  giving  the  effect  shown  in  Fig.  20.  Such  built  up  collars  make 
extremely  strong  joins.  Shafts  may  be  pushed  through  nitrate 
Pelton  wheels,  or  film  developing  drums,  and  secured  at  each  contact 
by  some  modification  of  the  procedure.  Good  contact  can  often  be 
made  between  a  glass  tube  and  a  single  plate  of  the  rotor  by  merely 
denting  the  glass  at  the  junction  and  painting  it  liberally  with  thick 
cement.  This  dries  into  the  hollow  and  produces  firm  adhesion. 

Steel  and  copper  offer  no  especial  difficulties  except  that  the  cement 
must  on  no  account  contain  acetic  or  other  acid. 

A  device  that  has  proved  useful  is  shown  in  Fig.  21.     A  spiral  of 

FIG.  23.     Model  of  film  developing  drum. 

narrow  nitrate  tube  was  wanted.  Accordingly,  a  coil  of  fine  copper 
piping,  having  an  outside  diameter  equal  to  the  internal  diameter 
of  the  finished  tube,  was  wound  into  a  well-spaced  spiral  and  sup- 
ported by  a  wire  handle.  It  was  then  dipped  about  30  times  into 
thick  nitrate  cement,  allowing  at  least  three  hours  for  drying  between 
successive  dips.  The  dipping  required  rigid  adherence  to  a  certain 
sequence  of  operations.  First,  the  spiral  was  dipped  with  a  slanting 
motion  into  thin  cement  and  quickly  withdrawn.  It  was  then 
instantly  lowered  slowly  in  a  slanting  manner  into  the  thick  cement. 
When  under  the  surface  it  was  rotated  through  180  degrees  and 
removed  at  an  angle,  being  careful  that  each  convolution  left  the  sur- 
face without  forming  a  drop.  Once  out  in  the  air,  it  was  rotated  in 
all  directions  for  a  minute  or  two  until  the  new  layer  had  set.  It 
was  then  hung  up  to  dry. 

Mar.,  1933] 



After  the  thirtieth  coat,  it  was  dried  for  a  day  in  the  60°C.  oven. 
The  copper  spiral  was  then  dissolved  out  with  1 : 1  nitric  acid.  This 
was  a  tedious  operation,  owing  to  the  driving  of  the  acid  out  of  the 
spiral  by  the  gases  formed.  It  has  to  be  done  quickly  or  degrada- 
tion of  the  nitrate  base  sets  in.  Finally,  when  the  copper  was  entirely 
removed,  a  mixture  of  water  with  25  per  cent  industrial  alcohol  was 
drawn  through,  a  few  cc.  per  minute,  for  a  day.  The  spiral,  when 

FIG.  24.     Complex  model  of  industrial  instrument. 

dried,  served  its  purpose  sufficiently  well.  One  is  shown,  minus 
the  copper  core,  at  the  right  of  Fig.  21. 

Strength  and  Rigidity. — Thin  nitrate  sheet  is  too  flexible  to  be 
mechanically  rigid  unless  it  is  bent  and  secured  in  many  directions. 
A  careful  design  will  include  sufficient  cross  pieces.  When  these 
are  not  admissible,  right-angle  struts  and  bracings  may  be  put  across 
the  straight  sides.  They  will  be  observed  in  some  of  the  later 

Tinting. — Both  nitrate  and  acetate  base  may  be  colored  by  dyes 
dissolved  in  a  mixture  of  alcohol  and  acetone.  The  particular  mix- 


ture  of  solvents  must  be  found  to  suit  the  individual  worker.  Gen- 
erally speaking,  the  more  acetone,  the  more  strongly  the  color  will 

Sphere  of  Usefulness. — In  the  laboratory  we  have  found  the 
construction  described  here  useful  for  making : 

Models  of  crystals  and  atoms,  where  it  is  desired  to  see  top,  bottom, 
and  contents,  all  at  the  same  time  (Fig.  22) . 

Film  developing  drums,  for  use  in  those  photographic  researches 
where  it  is  inadvisable  to  let  the  developer  touch  anything  but  glass 
and  film  substance  (Fig.  23) . 

Containers  in  hydraulic  systems,  where  it  is  necessary  to  observe 
the  path  taken  by  the  water. 

Certain  industrial  instruments,  where  the  solutions  attack  metals 
(Fig.  24). 

A  more  ambitious  use  is  found  in  the  construction  of  architects' 
models,  and  for  the  building  of  miniature  movie  sets.  The  architect 
has,  in  the  past,  been  content  to  build  his  miniatures  from  pasteboard 
which,  though  excellent  for  exteriors,  gives  the  patron  little  idea  of 
the  internal  lay-out.  It  is  possible  to  build  cottages  or  even  towns 
from  nitrate  or  acetate  stock,  and  show  a  superior  external  surface 
and  a  full  view  of  the  interior  arrangements. 

A  Word  of  Caution. — Acetate  sheeting  is  generally  a  trifle  less 
transparent  and  less  easy  to  work  than  nitrate  sheeting.  It  is  to  be 
preferred,  however,  for  all  large  construction  work  because  of  its 
safety.  Both  materials  shrink  with  age,  the  contraction  being 
most  marked  at  the  joints.  The  less  liberally  the  solvent  or  cement 
is  applied  during  construction,  the  less  serious  will  be  the  distortion. 
Simple  pieces  of  apparatus  may  have  a  life  of  years,  but  heavy 
cemented  pieces  of  unusual  shape  are  likely  to  present  a  distorted 
appearance  at  the  end  of  a  few  months. 




Summary. — The  motion  picture  as  it  is  known  today  has  existed  less  than  fifty 
years  but  certain  of  the  principles  which  underlie  its  development  can  be  traced 
back  many  years  more.  This  paper  represents  an  attempt  to  list  chronologically 
the  chief  devices  and  inventions  pre-dating  the  motion  picture  equipment  of  1895. 

25,000  B.C. — The  earliest  known  example  of  motion  expressed 
pictorially  was  found  in  a  cave  at  Altamira,  Spain,  representing  a 
trotting  bear  having  two  sets  of  legs,  probably  an  attempt  to  repre- 
sent the  one  set  of  legs  in  two  different  positions ;  the  relic  was  found 
in  rocks  of  the  Upper  Paleolithic  period,  and  probably  was  the  work 
of  a  Cro-Magnon.1 

5000  B.C.  et  seq— Ombres  Chinois,  "Chinese  Shadow  Shows."  All 
races  have  evolved  shadow  shows,  indicating  the  general  thought  to 
represent  motion  pictorially.  Records  exist  of  shadow  shows  in 
Egypt  and  India  before  the  time  of  Christ.  Historical  records  indi- 
cate that  in  Java  shadow  shows  were  included  in  every  festival. 
The  shadow  shows,  termed  wajang,  employed  miniature  figures 
grotesquely  made  of  leather,  cardboard,  wood,  or  other  mate- 
rials, the  shows  revolving  about  the  Javanese  customs  and  myths, 
gods  and  devils.  The  operator,  or  gamelong,  manipulates  the  figures 
before  a  fire,  so  as  to  throw  the  shadows  of  the  figures  upon  a  screen, 
accompanying  the  movements  with  suitable  conversation  and  music 
furnished  by  reeds  and  gongs.  The  audience,  squatted  before  the 
screen,  views  a  realistic  representation  of  the  conflicts  between  gods 
and  devils. 

In  France,  in  1767,  Seraphim  presented  shadow  shows  by 
means  of  a  magic  lantern.  The  series  was  popularly  known  as 
Chinese  Shadow  Shows,  or  Ombres  Chinois.  Caran  d'Ache  de- 
veloped these  shows  further,  establishing  them  as  French  Shows,  and 
presented  historical  tableaus.  Color  was  introduced  by  Henri 

*  Honorary  Curator,  Motion  Picture  Collections,  Los  Angeles  Museum,  Los 
Angeles  Calif. 


250  EARL  THEISEN  [j.  s.  M.  p.  E. 

Riviere  by  adding  colored  bits  to  the  figures;  he  tried  also  to  arrange 
the  figures  so  as  to  provide  perspective  in  the  shadows  by  using  two 
lanterns  so  arranged  as  to  present  dissolving  views. 2>3>4>6 

65  B.C. — Titus  Lucretius  Cams6  in  De  Rerum  Natura  wrote  as 
follows : 

"Do  not  thou  moreover  wonder  that  the  images  appear  to  move, 
And  appear  in  one  order  and  time  their  legs  and  arms  to  use. 
For  one  disappears,  and  instead  of  it  appears  another, 
Arranged  in  another  way,  and  now  appears  each  gesture  to  alter, 
For  you  must  understand  that  this  takes  place  in  the  quickest  time." 

This  is  probably  the  earliest  recorded  discussion  of  pictorially 
represented  motion.  From  this  record  it  would  seem  that  some 
kind  of  device  for  depicting  motion  existed  at  that  time. 

130  A.D. — A  record  of  this  date  of  a  device  for  depicting  motion 
exists  in  the  Bodleian  Library,  Oxford.7 

1640  A.D. — About  this  time  the  Magia  Catoptrica,  also  known  as 
the  Megaloscope,  was  invented  by  Athanasius  Kircher.  This  device 
was  a  lantern,  similar  to  the  present-day  magic  lantern,  with  which 
were  projected  drawings.  A  favorite  subject  for  projection  was  a 
drawing  of  the  devil  with  his  trident.  Kircher  wrote  a  book  entitled 
Ars  Magna  Lucis  et  Umbrae  (Great  Art  of  Light  and  Shadow)  in  1646. l 

1806. — Henry  L.  Child's  invention  of  the  Phantasmagoria,  or 
Bi-  Unial  Lantern,  was  announced  about  this  time.  The  device  was 
used  to  entertain  audiences  nightly  at  the  Sanspareil  Theater,  London, 
now  known  as  the  Adelphi.  Subsequently  there  appeared  a  great 
number  of  magic  lanterns  and  slide-shows  of  hand-drawn  trans- 

1824  (Dec.  9). — Peter  Mark  Roget  read  before  the  Royal  Society 
in  London  a  paper  describing  the  principle  of  persistence  of  vision, 
using  for  illustration  a  revolving  and  progressing  wheel,  the  spokes 
of  which  could  be  seen  through  a  vertical  aperture  placed  in  front  of 
the  wheel.8 

1826. — The  Thaumatrope  was  invented  about  this  time  by  John 
Ayrton  Paris.9  This  device  was  similar  to  one  made  several  months 
before  by  Dr.  W.  H.  Fitton  at  the  suggestion  of  Sir  John  Herschel.10 
It  consisted  of  a  cardboard  disk  with  two  strings  attached  to  the 
edges.  One  side  showed  the  picture  of  a  bird,  the  other  side  a  picture 
of  a  bird-cage.  Upon  spinning  the  disk,  the  bird  appeared  to  the 
onlookers  as  though  it  were  in  the  cage.  This  is  said  to  be  the  first 
device  that  depended  for  its  operation  upon  the  persistence  of  vision. 


1831. — The  physical  and  visual  phenomena  of  motion  were  studied 
by  Michael  Faraday,  in  England,  by  means  of  a  series  of  geared 
wheels,  one  combination  being  known  as  "Faraday's  Wheel."11 

1831. — The  Phenakisioscope,  later  known  as  the  Phantascope,  was 
invented  by  Joseph  Antoine  Ferdinand  Plateau.12  This  device  was 
composed  of  two  disks  revolving  together  on  a  single  shaft ;  one  disk 
had  a  series  of  slits  around  its  periphery,  the  other  a  series  of  drawings, 
in  phases,  of  a  complete  movement  or  action.  When  the  disks,  con- 
taining the  slits  and  drawings,  were  revolved,  the  appearance  of 
motion  was  obtained  by  looking  through  successive  slits  as  they 
passed  a  given  point.  Plateau,  in  Belgium  in  1843,  lost  his  sight  as 
a  result  of  his  experiments  in  vision. 

1832. — A  Stroboscopic  Device  was  invented  by  Dr.  Simon  Ritter 
von  Stampfer,  in  Austria,  which  was  identical  with  Plateau's  device, 
although  Plateau  and  von  Stampfer  worked  independently  of  each 

1834. — The  Daedaleum,  or  Wheel  of  the  Devil,  was  invented  by 
William  George  Horner,  of  England.  This  device  was  a  slitted 
cylinder,  mounted  on  a  stand,  through  the  slits  of  which  could  be 
seen  drawings  mounted  within. 

1850. — Perret  and  Lacroix  improved  the  Phantascope  by  adding 
to  it  a  front-slotted  disk,  the  first  to  be  used. 

1853. — Kircher's  magic  lantern  and  von  Stampfer's  motion  device 
were  combined  into  a  single  instrument  by  Lieut.  Baron  Franz  von 
Uchatius,  for  the  purpose  of  showing  the  trajectory  of  bullets;  this 
was  the  first  time  that  pictures  showing  motion  were  projected. 

1860. — The  Zootrope,  or  Wheel  of  Life,  was  patented  in  France  by 
Desvignes.  This  device  should  probably  be  regarded  as  the  fore- 
runner of  the  motion  picture  due  to  its  great  popularity  at  this  time. 
Galloping  horses  formed  the  favorite  subject  for  exhibition.13 

1861. — Dumont  patented  in  England  a  device  for  exhibiting 
motion  that  consisted  of  a  series  of  photographs  arranged  as  facets  on 
a  prismatic  drum  made  of  glass.14 

1861  (Feb.  5).— Coleman  Sellers  patented  in  the  United  States  the 
Kinematoscope.™  Photographs  of  his  children  were  made  in  suc- 
cessive phases  of  action  by  means  of  a  camera  having  two  lenses,  the 
photographs  thus  being  stereoscopic;  these  photographs  were  then 
mounted  seriatim  on  the  blades  of  a  paddle,  and  were  viewed  through 
a  stereoscope  while  moving  away  from  the  viewer  as  the  paddle  was 
turned  by  hand.  Action  was  thus  built  up  during  the  exposure  pose 

252  EARL  THEISEN  [j.  s.  M.  p.  E. 

by  pose;  the  wet  plates  were  kept  moist  with  glycerin  between 
poses,  dry  plates  having  not  yet  been  invented.  In  the  name  of  this 
instrument  the  word  kinema  was  used  for  the  first  time  in  connection 
with  pictures  of  moving  objects. 

1864  (Apr.  25). — Louis  Arthur  Ducos  du  Hauron  was  granted  a 
French  patent  on  a  device  operating  on  the  principle  of  persistence 
of  vision. 

1865. — In  France,  Omnius  and  Martin  photographed  the  beating 
heart  of  an  animal,  recording  the  beats  in  diagrammatic  form. 

1866. — J.  A.  R.  Rudge  succeeded  in  photographing  successive 
phases  of  motion;  exhibiting  in  1868  the  scenes  so  taken  with  his 
Bio-Phantascope,  or  lantern.  Two  of  the  mechanisms,  notably  a 
shutter  and  an  intermittent  movement  used  by  him  in  the  design  of 
this  lantern  projector,  are  similar  in  principle  to  those  employed  later 
by  others  in  connection  with  motion  picture  apparatus.  Rudge,  in 
1885,  became  associated  with  Friese-Greene. 

1866. — Beale  invented  the  Choreutoscope.1 

1867  (Apr.  23). — A  patent  was  granted  to  William  Lincoln  in  the 
United  States  on  a  device  known  as  the  Zootrope,  similar  to  Desvignes' 

1869. — Linnet  patented  his  Kineograph,  a  device  in  the  form  of  a 
book,  for  showing  pictures  of  moving  objects.  The  principle  of  this 
device  was  employed  in  the  Biograph  Company's  Mutoscope. 

1869. — Trevor  patented  a  system  of  taking  radial  photographs 
rapidly  on  glass. 

1870  (Feb.  5). — The  Phasmatrope,  invented  by  Henry  Renno 
Heyl,  was  exhibited  on  this  date  at  the  Academy  of  Music  at  Phila- 
delphia. It  was  a  device  having  pictures  on  glass,  mounted  radially 
on  a  wheel,  which  pictures  were  exposed  successively  and  intermit- 
tently to  the  rays  of  a  lantern  by  a  cam  and  pawl  mechanism.  The 
instrument  embodied  many  of  the  principles  of  the  present-day  pro- 
jector. As  his  first  subject  Heyl  chose  a  pair  of  dancers  waltzing, 
the  results  being  exhibited  at  the  Academy  to  an  audience  of  1600 

1871. — Thomas  Ross  announced  his  Wheel  of  Life. 

1872. — At  Leland  Stanford  University,  Eadweard  Muybridge 
produced  photographs  of  trotting  horses,  using  five  cameras  placed 
side  by  side.  The  culmination  of  his  experimental  work  occurred  in 
collaboration  with  John  D.  Isaacs.19 

1874. — Janssen  developed  the  photographic  pistol,  employing  a 


single  lens  and  one  plate ;  it  was  used  for  astronomical  purposes  only, 
particularly  for  taking  pictures  of  the  planet  Venus  in  its  successive 

1876. — A  device  for  tripping  cameras,  somewhat  similar  in 
arrangement  to  the  electrical  door-bell,  was  developed  by  John  D. 
Isaacs,  working  in  conjunction  with  Muybridge.  In  this  device  was 
used  a  shutter  patented  in  England  in  1856  by  Thomas  Skaife.  The 
number  of  cameras  used  for  photographing  the  trotting  horses  was 
increased  from  five  to  twelve,  then  finally  to  twenty-four.  These 
cameras  faced  a  white  background  forty  feet  long.  As  the  cameras 
were  side  by  side,  the  horses  would  appear,  when  the  pictures  were 
projected,  as  though  they  were  kicking  past  the  background.18 

1877. — Emile  Reynaud  devised  the  Praxinoscope,  for  projecting 
upon  a  screen  pictures  drawn  on  a  continuous  band  of  a  substance 
called  crystalloid.  The  first  subject  so  produced  was  Poor  Pierrot, 
which  was  first  exhibited  at  the  ' 'Reynaud  Electrical  Theater." 
Reynaud  also  developed  a  device  similar  to  the  Zootrope,  with  a 
central  drum  of  faceted  mirrors.21 

1877. — Jean  Louis  Messonier  made  transparencies  of  Muy- 
bridge's  horse-pictures,  which  were  mounted  on  a  glass  disk  rotating 
before  a  slotted  opaque  disk  and  illuminated  by  a  lantern.  This 
device  was  known  as  the  Zoopraxoscope. 

1882. — Dr.  E.  J.  Marey  developed  the  photographic  gun.  This 
device  registered  on  a  glass  plate  12  successive  pictures  of  white  fig- 
ures against  a  black  background  at  a  speed  of  1/2ooth  second  for 
each  picture.20- 22>  23 

1882. — Van  Hoevenbergh  was  granted  a  patent  on  a  card- 
flipping  device.24 

1885. — William  Friese-Greene  exhibited  pictures  of  successive 
phases  of  motion,  photographed  by  the  Marey  method  on  a  single 
glass  plate.  In  1888  he  began  to  experiment  with  transparent 
sensitive  paper;  and  in  1889,  applied  jointly  with  Mortimer  Evans 
for  a  British  patent,  using  conceptional  drawings,  from  which  the 
apparatus  was  later  constructed.  He  was  also  granted  a  British 
patent25  on  stereo-motion  pictures  in  1893,  and  a  color  patent26  in 

1886  (Nov.). — Louis  A.  A.  Le  Prince  applied  for  an  American  pat- 
ent on  a  camera  having  sixteen  lenses  or  less  (specification  calls  for  six- 
teen lenses).  On  Jan.  10,  1888,  a  patent29  was  granted,  eliminating 
claims  on  one-  and  two-lens  cameras  because  of  the  interference  of 

254  EARL  THEISEN  [j.  s.  M.  P.  E. 

Dumont's  British  patent14  of  1861.  On  Nov.  16,  1888,  a  British 
patent  was  granted  to  Le  Prince  on  a  single-  and  multiple-lens 
camera  and  projector,  using  the  Geneva  movement.  Although  the 
Le  Prince  camera  was  never  exploited,  Le  Prince  experimented  with 
sensitized  paper  and  gelatin  bands  for  film  until  the  fall  of  1889, 
when  he  is  said  to  have  obtained  sensitized  celluloid.30 

1887. — Edison,  assisted  by  W.  K.  L.  Dickson,  began  his  experi- 
ments with  motion  devices.  In  August,  1889,  he  obtained  a  short 
length  of  sensitized  Tollable  film  on  a  nitrocellulose  base  from  George 
Eastman.31  The  Kinetoscope,  employing  a  non-intermittent  move- 
ment, was  demonstrated  at  West  Orange,  N.  J.,  on  Oct.  6,  1889.  A 
patent32  was  applied  for  on  a  camera  in  August,  1891,  and  granted  in 
August,  1897.  The  peep-show  Kinetoscope  began  its  commercial  ex- 
hibits at  1155  Broadway,  New  York,  N.  Y.,  on  April  14,  1894,  at  the 
Holland  Brothers'  Peep-Show  Parlor.  In  April,  1896,  Edison  acquired 
the  Jenkins-Armat  and  Armat  projector  patents,  constructed  a  projec- 
tor, and  began  exhibits  at  Koster  and  Bial's  Music  Hall  during  the 
week  of  April  23, 1896.  The  Projecting  Kinetoscope  was  made  in  1897. 
The  Edison  camera  of  1889  was  capable  of  photographing  forty 
pictures  per  second.33  Edison's  choice  of  the  picture  size  and  film 
width  as  well  as  four  perforations  to  a  frame  are  considered  by  many 
to  have  established  these  standards  for  the  industry  which  later 
developed  so  rapidly. 

1888  (June  13). — Wallace  Goold  Levinson  read  a  paper  before 
the  Brooklyn  Academy  of  Photography,  describing  his  invention,  a 
wheel  with  photographic  plates  moving  in  sequence. 

1889. — Anchiitz  devised  the  electrical  tachyscope,  a  large  wheel 
having  pictures  drawn  about  the  rim.1 

1893-4. — Exhibitions  are  claimed  to  have  been  given  in  Washing- 
ton, D.  C.,  by  C.  F.  Jenkins,  using  a  projector  designed  by  himself 
and  called  the  Phantoscope**  Mr.  Jenkins  is  said  to  have  begun 
experimenting  in  1890  on  cameras  for  photographing  pictures  in 
rapid  succession  and  to  have  devised  several  with  single-  as  well  as 
multiple-lens  systems.  In  1893,  he  built  the  Phantoscope*  which 
used  a  beater  movement.35  On  March  25,  1894,  he  entered  into 

*  The  Photographic  Times  (1894)  contains  a  picture  of  the  Phantoscope  camera 
and  a  series  of  pictures  made  with  it.  Also  the  following  "...  the  pictures  are 
reproduced  in  an  optical  lantern  upon  any  size  screen,  so  rapidly  that  the  eye 
does  not  see  the  pictures  except  as  one  continuous  picture  with  the  objects  ap- 
parently in  motion." 


partnership  with  T.  Armat  for  the  purpose  of  constructing,  exhibiting, 
and  promoting  the  device.  Models  were  constructed  and  taken  to 
the  Cotton  States  Exhibition  in  Atlanta,  Georgia,  in  October,  1895. 

1894  (Feb.  5). — Two  Kinetoscope  films  were  projected  by  J.  A. 
LeRoy  before  a  group  of  about  25  persons  assembled  in  H.  Riley's 
Optical  Shop,  16  Beekman  St.,  New  York.  The  projector  used  was 
designed  and  built  by  Mr.  LeRoy  who  had  previously  (1893)  built  a 
projector  which  handled  unperf orated  film.36 

1894  (Nov.). — Herman  Casler  obtained  a  patent37  on  a  card- 
flipping  device.    Pictures  of  successive  phases  of  motion  were  mounted 
on  a  geared  hub.     Several  other  patents  were  granted  to  Casler:  on 
a  sliding  device  that  flipped  pictures  of  successive  phases  of  motion, 
Nov.,  1895 ;38  on  a  hand-shaken  device  with  mounted  pictures;39  and 
in  May,  1897,  on  a  device40  similar  to  Coleman  Sellers'  Kinemato- 
graph  (1861),  although  Casler's  device  was  not  stereoscopic.     In 
February,    Casler   obtained   a   patent41   for    the    Mutoscope.     The 
Casler  patents  were  used  by  the  American  Biograph  Company  in 
their  peep-show  devices,  as  were  the  W.  K.  L.  Dickson  patents  of 
September,  1897.42 

The  American  Biograph  Company,  formed  by  H.  N.  Marvin, 
W.  K.  L.  Dickson,  E.  B.  Koopman,  and  Herman  Casler,  gave  an  ex- 
hibit with  the  Mutoscope,  using  a  screen,  at  Hammerstein's  Olympia 
Music  Hall  on  Oct.  12,  1896.  The  Mutoscope  contained  a  roller 
mechanism  that  intermittently  squeezed  the  film  to  move  it  for- 
ward, then  perforated  the  film  while  it  was  at  rest,  for  the  printing 
operation.  Litigation  later  proved  the  Biograph  friction  move- 
ment to  be  the  only  one  that  did  not  infringe  on  the  Edison  and 
Edison-Armat  patents.43'44'45'46'47  Illustrations  of  the  friction  device 
known  as  the  web  feeding  device  and  the  Biograph  apparatus  as  a 
whole  can  be  found  in  the  itemized  patent  specifications. 

1895  (Mar.  22). — Louis  and  August  Lumiere  publicly  demonstrated 
their  Cinemawgraphe  on  Mar.  22,   1895.     A  public  exhibition,  for 
which  an  admission  fee  was  charged,  took  place  at  the  Grand  Cafe  in 
Paris  on  Dec.  28,   1895.     Using  a  planetary  cam  movement,  the 
pictures  were  projected  to  a  screen.     The  Lumieres  obtained  celluloid 
from  the  United  States  and  sensitized  it.     Their  camera  photo- 
graphed sixteen  pictures  per  second.18 

1895  (Apr.  21).— Woodville  Latham  with  the  assistance  of  E.  A. 
Lauste  completed  the  Pantoptikon,  later  known  as  the  Eidoloscope. 
On  Apr.  21,  1895,  the  first  press  exhibit  of  pictures  projected  to  a 

256  EARL  THEISEN  [j.  s.  M.  P.  E. 

screen  by  this  continuous-movement  device  was  given  at  35  Frank- 
fort Street,  New  York,  N.  Y.  On  May  20,  1895,  commercial  exhibits 
began  in  a  storeroom  at  153  Broadway,  New  York.  The  patent 
specification48  applied  for  June  1,  1896,  lists  a  loop  device  later  known 
as  the  Latham  Loop.  This  patent  was  declared  invalid  in  litigation, 
later,  due  to  a  prior  reduction  to  practice  by  Thomas  Armat.49'50 

1895  (Sept.). — Thomas  Armat,  continuing  his  experiments  inde- 
pendently of  C.  F.  Jenkins,  completed  the  Vitascope  projector,  later 
commercially  manufactured  by  Thomas  A.  Edison,  after  Edison  had 
acquired  from  Armat  certain  patents  on  the  Geneva  star  movement51 
and  beater  movement.52  The  first  public  exhibition  of  the  Vitascope 
took  place  at  Koster  and  Bial's  Music  Hall,  April  23,  1896.53 

1895  (Oct.).— The  Robert  Paul  projector  was  perfected,  with  the 
assistance  of  Birt  Acres.18  A  demonstration  was  held  at  the  Royal 
Institute,  London,  on  Feb.  28,  1896.  The  first  experiments  con- 
cerned continuous  movements,  but  finally  the  seven-point  Maltese 
Cross  was  incorporated  in  the  mechanism  and  successful  exhibits 
were  held. 


1  DAY,  W.  E.  I.:    "Illustrated  Catalog  of  the  Will  Day  Historical  Collection 
of  Cinematograph  and  Moving  Picture  Equipment,"  London,  1930. 

2  La  Nature,  No.  777,  France  (Apr.,  1888),  pp.  521,  522. 

3  RAFFLES,  THOMAS  S.:    "History  of  Java,"  Vol.  I,  John  Murray,  London 
(1817),  pp.  336,  338. 

4  ZIEGLER,  FRANCIS  J.:      "Puppets,  Ancient  and  Modern,"  Harper's  News 
Monthly  96,  (1896)  p.  85. 

5  "Parlour  Magic — Chinese  Shadow  Shows,"  5th  ed.,  W.  Kent  &  Co.,  London, 
(1861),  pp.  56,  58. 

6  CARUS,  TITUS  LUCRETIUS:   De  Rerum  Natura. 

7  Martin  Duncan's  Lecture  (Nov.  22,  1905),  Society  of  Arts,  London. 

8  ROGET,  PETER  MARK:    "Explanation  of  an  Optical  Deception  in  the  Appear- 
ance of  the  Spokes  of  a  Wheel  Seen  Through  Vertical  Apertures,"  Phil.  Trans. 
Royal  Society,  115  (1825),  pp.  131-40. 

9  PARIS,  J.  A.:    "Philosophy  in  Sport  Made  Science  in   Earnest,"  3  vols., 
London  (1827).     Copies  in  collection  of  W.  Day.     See  Ref.  1. 

10  BABBAGE,  CHAS.:   "Passages  from  the  Life  of  a  Philosopher,"  London,  1864. 
Copy  in  collection  of  W.  Day.     See  Ref.  1. 

11  FARADAY,  M.:    "On  a  Peculiar  Class  of  Optical  Deception,"  /.  Royal  In- 
stitution, 1  (N.  S.)  (1831),  p.  205. 

12  PLATEAU,  J.  A.  F.:    "Lettre  sur  une  Illusion  d'Optique,"  Ann.  de  Chimie 
et  de  Phys.  (2)  XLVHI  (1831),  p.  281. 

13  MATHEWS,  BRANDER:    "The  Forerunner  of  the  Movies,"  Century,  87  (Old 
Series)  or  65  (N.  S.),  April,  1914,  p.  916. 

14  Brit.  Pat.  1457. 


16  U.  S.  Pat.  31,357. 

16  U.  S.  Pat.  64,117. 

17  Luxz,  E.  G.:   "Animated  Cartoons,"  Chas.  Scribner's  Sons,  New  York,  1920, 
p.  29. 

18  RAMSAYE,  TERRY:    "A  Million  and  One  Nights,"  Vol.  I,  Simon  &  Schuster, 
New  York,  1926,  p.  18. 

19  MUYBRIDGE,  EADWEARD:    "Horse  in  Motion,"   University  of  Pennsylvania, 

20  Cassell's  Encyclopedia  of  Photography,  14th  Ed.,  1912. 

21  "Le  Theatre  Optique,"  La  Nature,  Part  2,  France,  1892,  p.  127. 

22  TALBOT,  F.  A.:    "Moving  Pictures,"  Lippincott  Co.,  Philadelphia,  Pa.,  1912, 
pp.  13,  18. 

23  MAREY,  J.:    "La  Chronophotographie,"  Gauthier-Villars,  Paris,  1899. 

24  U.  S.  Pat.  259,950. 

25  Brit.  Pat.  22,954. 

26  Brit.  Pat.  21,649. 

27  Motion  Picture  News,  XII,  Aug.  11,  1911. 

28  "A  Machine  Camera  Taking  Ten  Photographs  a  Second,"  Scientific  Ameri- 
can, Supp.,  XXIX  (Apr.  19,  1890),  No.  746,  p.  11,921. 

29  U.  S.  Pat.  376,247. 

30  SCOTT,  E.  K.:    "Career  of  L.  A.  A.  Le  Prince,"  /.  Soc.  Mot.  Pict.  Eng., 
XVH  (July,  1931),  p.  46. 

31  ACKERMAN,  C.  W.:    "George  Eastman,"  Houghton  Mifflin  Co.,  New  York, 
1930,  p.  277. 

32  U.  S.  Pat.  589,168. 

33  DICKSON,  W.  K.  L.:    "History  of  the  Kinetograph,"  A.  Bunn,  New  York, 

34  RICHARDSON,  F.  H.:    "What  Happened  in  the  Beginning,"  Trans.  Soc.  Mot. 
Pict.  Eng.  (1925),  No.  22,  p.  63. 

35  JENKINS,  C.  F.:    "Animated  Pictures,"  H.  L.  McQtieen,  Washington,  D.  C., 
1898,  pp.  26-44.     U.  S.  Pats.  536,569  and  560,800;    also  "Chronophotography," 
The  Photographic  Times,  25  (July  6, 1894),  p.  2. 

36  CRAWFORD,  M.:    "J.  A.  LeRoy — Projection  Pioneer,"  J.  Soc.  Mot.  Pict. 
Eng.,  XVI  (Jan.,  1931),  No.  1,  p.  109. 

37  U.  S.  Pat.  549,309. 

38  U.  S.  Pat.  584,305. 

39  U.  S.  Pat.  614,367. 

40  U.  S.  Pat.  597,795. 

41  U.  S.  Pat.  652,796. 

42  U.  S.  Pats.  636,500  and  636,642,  Sept.,  1897. 

43  U.  S.  Pats.  611,590  and  611,591;   Patent  Gazette,  No.  84,  p.  2006. 

44  U.  S.  Pat.  636,717,  May  9,  1899;   U.  S.  Pat.  636,715,  Mar.  11,  1899. 

45  "The  Court  Decision  in  Patent  Case,"  The  Bill  Board,  XIX  (Mar.  16,  1907), 
No.  17,  pp.  56,  140. 

40  Motion  Picture  News  (Feb.  15,  1913),  p.  685. 

47  "The  Art  of  Moving  Pictures,"  Scientific  American,  LXXVI  (Apr.  17,  1897), 
No.  17. 

48  U.  S.  Pat.  707,934. 


49  New  York  Sun,  Apr.  21,  1895. 

50  HOPWOOD,  HENRY  V.:    "Living  Pictures,"  Optician  and  Phot.  Trades  Review, 
London,  1899;   also  2nd  ed.,  The  Hatton  Press,  London,  1915. 

"  U.  S.  Pat.  578,185. 

"  U.  S.  Pat.  673,992,  Feb.  19,  1896. 

53  Morning  Times,  Washington,  D.  C.,  Oct.  14,  1896. 


"La  Chronophotographie,"  by  L.  GASTINE,  Gauthier-Villars,  Paris,  1897. 

"Picture  Ribbons,"  by  C  F.  JENKINS.  Published  by  C.  F.  Jenkins,  Washing- 
ton, D.  C.,  1897. 

"Animated  Pictures,"  by  C.  F.  JENKINS.  Published  by  C.  F.  Jenkins,  Wash- 
ington, D.  C.,  1898. 

"La  Photographic  Animee,"  by  E.  TRUTAT,  Gauthier-Villars,  Paris,  1899. 

"La  Chronophotographie,"  by  J.  MAREY,  Gauthier-Villars,  Paris,  1899. 

"Living  Pictures,"  by  H.  V.  HOPWOOD,  Optician  and  Photographic  Trades 
Review,  London,  1899.  Contains  an  excellent  review  of  early  patent  literature. 
(Revised  1912  and  1915.) 

"Die  Kinematographie,"  by  K.  W.  WOLF-CZAPEK,  Union  Deutsche  Verlags., 
Dresden,  1908. 

"Motion  Picture  Work,"  by  D.  S.  HULFISH,  American  School  of  Correspondence, 
Chicago,  1913. 

"Wissenschaftliche  Kinematographie,"  by  F.  P.  LIESEGANG,  E.  Liesegang, 
Diisseldorf,  1920. 

"Moving  Pictures — How  They  Are  Made  and  Worked,"  by  F.  A.  TALBOT, 
Lippincott  Co.,  Philadelphia,  1923. 

"Histoire  du  Cinematographe,"  by  G.  M.  COISSAC,  Gauthier-Villars,  Paris 

"A  Million  and  One  Nights— The  History  of  the  Motion  Picture,"  by  T. 
RAMSAYE,  2  vols.,  Simon  &  Schuster,  New  York,  1926. 

"Geschichte  der  Kinematographie,"  by  WILHELM  DOST,  W.  Knappe,  Halle, 

"The  Will  Day  Historical  Collection  of  Cinematograph  and  Moving  Picture 
Equipment."  Book  of  Sales  dated  Jan.  21,  1930.  Solicitors,  Bulcraig  &  Davis, 

"A  History  of  the  Movies,"  by  B.  B.  HAMPTON,  Covici-Friede,  New  York, 



Summary. — The  following  chronology  deals  with  the  evolution  of  motion  pictures 
as  produced  photographically  on  a  nitrocellulose  support  carrying  a  light-sensitive 
emulsion  of  one  kind  or  another.  Even  though  the  later  dates  of  the  preceding  chro- 
nology overlap  the  earlier  dates  of  the  one  that  follows,  the  two  chronologies  have  been 
kept  distinct  in  order  to  present  the  history  of  the  nitrocellulose  film  base  as  a  unit  in 


1845-6. — The  discovery  of  the  cellulose  nitrates  about  this  time  is 
credited  to  Schoenbein,  who  became  associated  with  Bottger  some- 
time subsequently  to  August,  1846. 1>2 

1847. — The  solubility  of  the  cellulose  nitrates,  especially  in  alcohol 
and  ether,  was  accurately  investigated  by  Gladstone;  these  experi- 
ments no  doubt  led  to  the  subsequent  discovery  of  collodion.1 

1848. — Iodized  collodion  was  used  by  Frederick  Archer  Scott  in  his 
calotype  wet-plate  process.3 

1855. — Alexander  Parkes  was  granted  an  English  patent  on  parke- 
sine,  a  substance  similar  to  collodion,  made  by  mixing  anhydrous 
wood  alcohol  with  guncotton.4 

1868. — Daniel  Spill  invented  xylonite,  a  combination  of  pyroxylind, 
alcohol,  and  ether;  he  was  associated  with  Parkes  in  some  of  his 

1869.— John  W.  Hyatt,  of  Newark,  N.  J.,  invented  celluloid  by 
combining  collodion  with  camphor,  for  which  he  was  granted  a 
U.  S.  patent6'7  on  June  15,  1869;  in  the  patent  specifications  the  name 
pyroxylin  was  used.  Numerous  patents  were  granted  to  the  Hyatt 
brothers  covering  various  uses  of  this  material  as  artificial  ivory. 
The  name  celluloid  first  appeared  in  the  U.  S.  Patent  Gazette 
on  July  2,  1872,  in  the  name  of  the  Celluloid  Manufacturing 
Company,  of  Albany,  N.  Y.,  assignee  of  the  various  Hyatt  pat- 
ents. 8>9'10 

*  Honorary  Curator,  Motion  Picture  Collections,  Los  Angeles  Museum, 
Los  Angeles,  Calif. 


260  EARL  THEISEN  [J.  S.  M.  p.  E. 

1876. — On  November  9  of  this  year,  an  English  patent11  was  issued 
to  Wordsworth  Donisthorpe  on  the  Kinesograph,  a  device  to  be  used 
for  taking  photographs  on  glass  plates  arranged  as  a  pack,  each  plate 
dropping  out  of  the  way  of  the  succeeding  plate  after  being  exposed. 
Pictures  were  taken  at  the  rate  of  eight  a  second.  The  patent 
specified  that  the  pictures  were  to  be  finished  on  paper  and  spaced 
equidistantly  thereon.  Another  patent  was  granted  to  Donisthorpe 
on  August  15,  1889,  specifying  the  use  of  an  electric  spark  for  pro- 
viding intermittent  illumination  in  a  viewing  device.  In  La  Nature12 
appears  the  following  description  of  Donisthorpe's  work:  "If  the 
apparatus  be  arranged  to  take  the  successive  pictures  at  sufficiently 
short  intervals  of  time  they  may  be  printed  at  equal  distances  upon  a 
continuous  strip  of  paper;  this  paper,  with  the  whole  series  of  pic- 
tures upon  it,  may  be  used  in  the  instrument  known  as  the  Zootrope 
or  Phenakistoscope.  .  .  this  strip  may  be  wound  on  a  cylinder,  to 
be  unwound  from  it  at  a  uniform  speed  to  another  cylinder,  and  so 
carried  on  past  the  eye  of  the  observer,  any  ordinary  means  being 
used  for  insuring  that  the  picture  shall  be  exposed  only  momentarily 
to  the  observer.  By  this  means  the  movements  made  by  a  person 
or  group  of  persons,  or  any  other  object  during  the  time  they  were 
being  photographed,  may  be  reproduced  to  the  eye  of  the  observer."13 

1884.— W.  H.  Walker  and  George  Eastman,  on  June  27,  1884, 
assigned  to  the  Eastman  Dry  Plate  &  Film  Company  a  patent 
application  on  the  process  of  coating  paper  with  an  emulsion  having 
a  soluble  under-coating  so  that  it  might  be  applied  to  a  stripping 
process;  granted  in  1890. 14 

1887. — Hannibal  Goodwin,  in  May  of  this  year,  applied  for  a  U.  S. 
patent  on  a  method  of  preparing  a  celluloid  support  for  photographic 
emulsions,  the  title  being  "Photographic  Pellicle  and  Method  for 
Producing  Same."  The  patent15  was  granted  on  September  13, 
1898;  it  is  said  that  Goodwin  did  not  reduce  it  to  practice.  This 
patent  was  later  the  subject  of  lengthy  litigation,  which  was  ulti- 
mately decided  in  favor  of  Goodwin's  successors.16'17 

1888. — John  Carbutt,  in  Philadelphia,  began  the  commercial 
manufacture  of  films  coated  on  sheet  celluloid,  obtained  from  a 
company  in  Newark,  N.  J.  He  apparently  experimented  with  this 
product  for  two  or  three  years  before  he  could  make  it  commercially.18'19 

1888. — Wallace  Gould  Levinson  on  June  26  applied  for  a  U.  S. 
patent,20  which  was  subsequently  granted,  describing  further  de- 
velopments along  these  lines. 


1889. — On  April  9,  Harry  M.  Reichenbach  applied  for  a  U.  S.  pat- 
ent, which  was  granted  on  December  10,  on  a  method  of  making 
transparent  sheets  of  celluloid;  a  mixture  of  methyl  alcohol,  camphor, 
nitrocellulose,  amyl  acetate,  and  fusel  oil  was  dried  on  a  polished 
support,  after  which  it  was  stripped  off  and  coated  with  the  photo- 
graphic emulsion.  This  patent  was  assigned  to  the  Eastman  Dry 
Plate  Company.  The  apparatus  for  coating  the  film  base  was  pat- 
ented by  Eastman  on  March  22,  1892. 21  According  to  present 
records,  the  first  supply  of  this  stock  to  be  used  for  producing  suc- 
cessful motion  pictures  was  sent  to  W.  K.  L.  Dickson  at  the  Edison 
Laboratories  in  July  or  August,  1889. 18>  22 

1891. — Eastman  daylight-loading  roll  introduced. 

1895. — In  August,  Eastman  introduced  the  first  positive  motion 
picture  stock;  prior  to  this  time  motion  pictures  were  made  on  nega- 
tive film,  which  could  be  bought  in  100-foot  lengths.  Many  experi- 
menters in  Europe  at  this  time  bought  the  Eastman  uncoated  nitro- 
cellulose film  bare  and  coated  it  themselves,  notably  the  Lumiere 
brothers  in  France. 

1903. — Eastman  introduced  film  having  a  gelatin  coating  on  the 
rear  surface  in  order  to  counteract  curling  of  the  film;  the  process 
had  been  patented  by  him  in  1890. 

1904. — W.  C.  Parkin,  in  France,  was  granted  a  patent23  on  a  method 
of  making  celluloid  non-inflammable  by  adding  a  soluble  metallic  salt  to 
ordinary  celluloid.  Subsequently,  many  others,  chiefly  in  France,  were 
granted  patents  on  various  ways  of  rendering  celluloid  non-inflammable 
or  slow-burning,  by  means  of  adding  various  metallic  salts.24 

1913. — In  September,  Eastman  introduced  panchromatic  negative 
motion  picture  film. 

1919. — Eastman,  introduced  for  the  first  time  film  that  had  latent 
image  footage  numbers  printed  on  its  edge;  the  markings  included 
also  the  date,  which  was  later  omitted,  and  the  markings  evolved  into 
the  form  as  used  today.  The  system  was  patented  by  Joseph  Aller 
in  1922,  the  application  being  made  in  1917. 

1921. — On  March  1,  Eastman  introduced  colored  base  positive  raw 
stock  in  nine  colors:  orange,  amber,  light  amber,  yellow,  pink,  red, 
green,  blue,  lavender,  in  addition  to  clear  (black  and  white).  Prior 
to  this  time,  colored  stock  had  been  made  in  the  various  finishing 
laboratories  by  dyeing  the  emulsion  after  the  processing  of  the  picture. 

1923. — In  January  Eastman  introduced  the  16-mm.  reversal  film 
and  apparatus  for  amateur  use. 



1  WORDEN,  E.  C.:  "Nitrocellulose  Industry,"  D.  Van  Nostrand  Co.,  New  York, 
1911,  Vol.  I,  pp.  22-24. 

2  International  Encyclopedia,  2nd  ed.,  Vol.  IV,  Dodd,  Meade  &  Co.,  New  York, 
1920,  p.  753;  Encyclopedia  Britannica,  14th  ed.,  Vol.  5,  1929,  p.  97;  Encyclopedia 
Americana,  1932  ed.,  Vol.  6,  p.  175. 

3  The  Chemist,  1851. 

4  WORDEN,  E.  C.:  "Nitrocellulose  Industry,"  D.  Van  Nostrand  Co.,  New  York, 
1911,  Vol.  II,  p.  568. 

6  Ibid.,  p.  571. 

6  U.  S.  Pat.  88,634. 

7  U.  S.  Pat.  91,341.     Method  of  Making  Solid  Collodion. 

8  U.  S.  Pat.  91,233.     Process  and  Apparatus  for  Manufacturing  Pyroxyline. 

9  U.  S.  Pat.  133,229,  Nov.  19,  1872. 

10  WORDEN,  E.  C.:  "Nitrocellulose  Industry,"  D.  Van  Nostrand  Co.,  New  York, 
1911,  Vol.  II,  pp.  576-582. 

11  Brit.  Pat.  4344,  Nov.  9,  1876. 

12  La  Nature,  Jan.  24,  1878. 

13  JENKINS,  C.  F.:   "Animated  Pictures,"  H,  L.  McQueen,  Washington,  D.  C., 
1898,  pp.  26-44. 

14  U.  S.  Pat.  420,130. 

15  U.  S.  Pat.  610,861. 

16  ACKERMAN,  C.  W.:    "George  Eastman,"  Houghton  Mifflin  Co.,  New  York, 

17  WORDEN,  E.  C.":  Nitrocellulose  Industry,"  D.  Van  Nostrand  Co.,  New  York, 
1911,  Vol.  II,  p.  846. 

18  British  Journal  Photographic  Almanac,  1926,  p.  480. 

19  Philadelphia  Photographer,  25  (Nov.  3, 1888),  p.  672. 

20  U.  S.  Pat.  578,249. 

21  U.  S.  Pat.  471,469. 

22  RAMSAYE,  TERRY:    "A  Million  and  One  Nights,"  2  vols.,  Simon  &  Schuster, 
New  York,  1926. 

23  French  Pat.  344,501. 

24  BOCKMANN,    FRIEDRICH:      "Celluloid,    Its   Raw   Materials,    Manufacture, 
Properties,  and  Uses,"  translated  from  the  3rd  German  ed.,  by  H.  B.  Stocks; 
Scott  &  Co.,  London,  1921. 


SANFORD,  P.  G. :     "Celluloid,"  2nd  ed.,  Crosby,  Lockwood  &  Son,  London,  1906. 

CROSS,  C.  F.:     "Cellulose,"  Longmans  Green  &  Co.,  London,  1901. 

NEBLETTE,  C.  B.:  "Photography,  Its  Principles  and  Practice,"  D.  Van 
Nostrand  Co.,  New  York,  1927. 

WORDEN,  E.  C.:  "Nitrocellulose  Industry,"  2  vols.,  D.  Van  Nostrand  Co., 
New  York,  1911. 

C.    H.    BOTHAMLEY 

Summary. — The  author,  who  presided  over  the  meeting  of  the  Photographic  Con- 
vention of  the  United  Kingdom  at  Chester,  England,  in  1890,  describes  some  of 
the  work  of  E.  J.  Marey,  Muybridge,  Friese-Greene,  and  Le  Prince,  pioneers  in  the 
art  of  producing  and  exhibiting  motion  pictures.  The  information  given  in  this 
paper  is  particularly  interesting  in  view  of  the  personal  acquaintance  of  the  author 
with  these  pioneers  during  the  time  in  which  they  were  conducting  their  work. 

When  an  invention  or  development  in  pure  or  applied  science 
rapidly  receives  recognition  and  wide  application,  especially  if  it  be 
of  a  kind  that  achieves  popularity,  there  is  always  a  chance  that  the 
merits  of  the  pioneers  responsible  for  the  invention  or  development 
will  be  underestimated,  and  even  that  the  precise  part  that  they 
played  will  be  forgotten.  For  example,  though  the  name  of  E.  J. 
Marey,  Professor  in  the  College  of  France,  is  occasionally  mentioned, 
it  is  doubtful  whether  the  importance  of  his  work  is  fully  appreciated, 
notwithstanding  the  fact  that  his  book,  Le  Mouvement,  was  translated 
into  English  by  Dr.  Eric  Prichard,  and  published  in  1895.  It  is  not 
improbable  that  this  is  due  to  the  fact  that  Marey  restricted  himself 
to  his  original  line  of  work,  the  study  of  the  movements  of  living 
things,  from  the  scientific  rather  than  from  a  popular  point  of  view, 
and  his  book  is  a  somewhat  technical  account  of  his  results,  with 
illustrations  that  are  numerous,  but  on  a  small  scale. 

Marey  himself  states  that  the  real  originator  of  this  line  of  work 
was  the  famous  astronomer,  Janssen,  who,  in  December,  1874,  took  a 
series  of  successive  photographs  of  the  transit  of  the  planet  Venus 
across  the  face  of  the  sun.  A  rotating  circular  plate  was  used,  the 
interval  between  successive  exposures  being  seventy  seconds.  Jans- 
sen,  moreover,  suggested  that  this  method  of  making  successive  photo- 
graphs at  regular  intervals  might  be  applied  to  the  study  of  the  motion 
of  animals,  especially  of  locomotion. 

After  Janssen,  came  Eadweard  Muybridge  who,  about  the  year 
1880,  or  a  little  earlier,  at  the  suggestion  of  a  Mr.  Stanford,  a  former 

*  Reprinted  from  the  Photographic  Red  Book,  London  (1931),  p.  78. 


264  C.  H.  BOTHAMLEY  [J.  S.  M.  P.  E. 

Governor  of  California,  applied  the  principle  to  the  photographic 
study  of  the  movements  of  the  horse,  and  who  subsequently  ex- 
tended his  experiments  to  other  animals  and  to  human  beings.  As  is 
well  known,  Muybridge's  method  was  to  use  a  long  line  of  cameras, 
the  lenses  of  which  pointed  across  a  defined  track,  along  which  the 
object  moved,  the  successive  exposures  being  made  by  permitting 
the  moving  body  itself  to  operate  a  simple  system  of  shutter  releases. 
The  method  was  cumbersome,  being  limited  somewhat  severely  by 
the  number  of  exposures  possible,  but  the  results  were  very  striking 
and  valuable.  A  selection  of  them  can  be  seen  in  Muybridge's  book 
in  the  Library  of  the  Royal  Photographic  Society.  Much  new  light 
was  thrown  on  the  mechanics  of  walking  and  other  movements. 

Muybridge  was  able  to  demonstrate  his  results  by  means  of  the 
projection  lantern  and,  in  1889,  gave  lectures  at  Newcastle-on-Tyne 
and  at  other  places  in  the  north  of  England.  Professor  A.  Smithells, 
F.R.S.,  then  professor  of  chemistry  in  the  Yorkshire  College  (now 
Leeds  University),  persuaded  him  to  come  to  Leeds  and  give  a  demon- 
stration of  his  results.  I  met  Muybridge  on  that  occasion,  and  was 
able  to  give  him  some  help  in  setting  up  his  lantern  and  other  equip- 
ment. The  plates  carrying  the  successive  images  were  fixed  to  a 
large  glass  disk,  which  rotated  between  the  condenser  and  the  lens, 
while  an  opaque  disk  with  transparent  slits  in  it  rotated  in  the 
opposite  direction.  The  results  surprised  as  much  as  they  delighted 
the  large  and  somewhat  critical  audience  before  which  they  were 
shown.  Perhaps  the  most  striking  of  all  the  demonstrations  was 
that  of  the  wing  motion  of  a  large  white  bird  (a  cockatoo,  I  think). 
As  the  wing  moved  in  the  up-stroke,  brilliantly  lighted  by  sunshine, 
we  saw  most  distinctly  every  plume  of  tlie  wing  turn  on  its  base,  so 
as  to  present  only  its  edge  in  the  direction  of  motion,  and  thus  offer  as 
little  resistance  to  the  air  as  possible.  As  the  wing  came  down,  each 
plume  turned  back  so  as  to  present  its  flat  surface  to  the  air  and  thus 
gain  the  maximum  impulse.  I  well  remember  the  murmur  of  as- 
tonishment and  pleasure  that  went  through  the  whole  audience,  and 
the  persistent  demands  for  the  repetition  of  what  was  as  beautiful  a 
picture  as  I  have  ever  seen  on  a  screen. 

Marey  and  Muybridge  were  early  in  communication,  and  in  order 
to  obtain  simpler  and  more  portable  apparatus,  Marey  invented  his 
" photographic"  gun.  This  apparatus,  it  should  be  noted,  required 
only  one  lens.  It  was  built  in  the  form  of  an  ordinary  sporting  gun, 
but  of  course,  with  different  relative  dimensions  of  its  parts,  and  was 


used  on  the  shoulder  and  sighted  in  the  same  way  as  a  gun.  At  first, 
plates  were  used,  which  were  attached  to  a  disk  of  glass  contained  in  a 
drum  fixed  to  the  gun  just  as  a  revolver  barrel  would  be.  The  disk 
could  be  rotated  by  clockwork  actuated  by  the  gun-trigger.  The  ex- 
posure was  first  made;  then  the  shutter  closed,  and  the  disk  moved 
around  and  brought  another  plate  into  position.  With  this  ap- 
paratus, the  number  of  exposures  possible  was  12  per  second,  and  the 
plates  were  necessarily  very  small.  Soon,  "a  continuous  film  very 
slightly  coated  with  gelatin  and  bromide  of  silver"  was  substituted 
for  plates,  the  film  being  wound  on  bobbins,  at  the  end  of  which  were 
flat  plates  having  perforations  that  were  engaged  by  a  peg  in  a  metal 
plate  in  order  to  rotate  the  bobbin.  Black  paper  attached  to  the 
ends  of  the  film  made  filling  and  changing  possible  in  daylight. 
The  images  obtained  with  this  apparatus  were  9  centimeters  wide. 
The  improved  apparatus  and  the  increased  sensitivity  of  the  films  ob- 
tainable made  it  possible  to  study  the  movements  of  a  wide  variety 
of  living  beings,  the  results  of  which  study  are  set  out  in  the  book  to 
which  I  have  already  referred. 

In  a  delightful  place  in  Beaune,  bounded  on  one  side  by  one  of  the 
great  bastions  of  the  fortifications,  and  on  the  other  by  a  row  of  those 
dignified  renaissance  houses  that  give  a  distinct  cachet  to  this  quaint 
old  town,  there  is  a  railed-in  enclosure  planted  with  graceful  trees; 
in  their  midst  is  a  life-sized  statue  of  Marey,  a  sturdy  thick-set 
seated  figure  with  a  face  of  marked  character.  Against  the  figure  is  a 
mass  of  stone,  on  the  body  of  which  are  carved  representations  of  his 
pictures  of  horses;  while,  as  a  frieze,  there  is  a  representation  of  his 
study  of  a  flying  bird.  A  long  inscription  sets  out  the  achievements 
and  honors  of  this  distinguished  Professor  of  the  College  of  France, 
and  the  esteem  in  which  he  was  held  by  his  townsmen  and  country- 

Friese-Greene,  on  June  26,  1890,  at  a  meeting  of  the  Photographic 
Convention  of  the  United  Kingdom  at  Chester,  over  which  I  presided 
as  president  for  the  year,  read  a  paper  on  A  Magazine  Camera  and 
Lantern.  He  exhibited  and  described  the  camera  that  he  had  in- 
vented for  making  a  long  series  of  successive  exposures  on  a  sensitive 
film,  which  was  moved  by  means  of  perforations  in  the  film  itself, 
instead  of  by  perforations  on  a  bobbin.  He  likewise  exhibited  and 
described  a  lantern  that  he  had  devised  for  projecting  the  images  so 
obtained.  Unfortunately,  on  the  journey  from  London,  the  projec- 
tion apparatus  had  been  damaged  so  that  it  could  not  be  used,  and 

266  C.  H.  BOTHAMLEY 

the  films  that  Greene  had  brought  with  him  for  exhibition  could 
not  be  projected.  This  accident  and  the  non-descriptive  title  which 
he  gave  to  his  paper  were  most  unfortunate,  and  I  am  inclined  to 
doubt  whether  any  of  the  numerous  experienced  photographers  at  the 
meeting  quite  realized  what  a  distinct  advance  Greene  had  really 

It  is  a  point  of  interest  that  the  art  now  so  widely  applied  for 
purposes  of  entertainment  originated  from  a  desire  for  making 
scientific  investigations,  of  which  most  of  the  patrons  of  the  cinema  are 
probably  ignorant;  although  to  a  very  limited  extent  it  is  occasionally 
brought  to  their  notice  that  the  methods  used  to  produce  the  pictures 
that  amuse  them  are  still  constantly  employed  in  scientific  studies  of 
great  importance  from  various  points  of  view. 

Le  Prince,  whose  claims  as  one  of  the  pioneers  I  have  recently  ad- 
vanced, I  knew  well  by  sight ;  in  fact,  I  met  him  once  or  twice  at  the 
house  of  Mr.  and  Mrs.  Wilson,  with  whom  he  had  gone  abroad  just 
before  his  mysterious  disappearance.  I  have,  however,  no  recollec- 
tion of  having  heard  anything  about  his  work  in  kinematography  up 
to  the  time  when  I  left  Leeds  in  August,  1891,  although  I  was  a  fairly 
regular  attendant  at  the  meetings  of  the  Leeds  Photographic  Society. 
Probably  he  did  not  desire  publicity  until  he  had  made  satisfactory 
arrangements  for  working  his  patents. 


Making  Better  Movies.  A.  L.  GALE  AND  R.  C.  HOLSLAG.  Amateur  Cinema 
League,  Inc.,  New  York,  N.  Y.,  1932,  205  pp. ;  a  limited  edition  for  distribution  to 
members  of  the  League. 

The  purpose  of  the  book  is  to  unravel  some  of  the  mysteries  that  motion  pic- 
tures seem  to  hold  for  many  amateurs,  particularly  those  who  are  new  at  the 
work,  and  to  discuss  the  problems  of  "making  better  movies."  For  that  reason, 
it  is  written  in  a  rather  elementary  manner;  and  although  the  book  might  be  of 
questionable  value  to  professional  motion  picture  engineers,  it  should  be  of  inter- 
est to  those  engineers,  at  least,  whose  commercial  activities  bring  them  into  contact 
with  the  amateur  and  the  amateur  market,  so  that  they  may  be  fully  cognizant 
of  the  problems  facing  the  purchasers  and  users  of  their  equipment  and  material. 

Necessarily,  the  book  deals  with  16-mm.  film  and  equipment,  a  few  allusions 
being  made  to  the  8-mm.  systems.  The  nature  of  the  book  can  best  be  appre- 
ciated by  considering  its  contents :  Chapter  1  contains  an  introduction  to  the  sub- 
ject, instructions  on  how  to  handle  the  camera,  a  discussion  of  sizes  of  film,  expos- 
ing, stop  numbers,  lighting,  planning  the  picture,  footage,  etc.  The  second 
chapter  deals  with  handling  the  projector,  caring  for  the  film,  editing,  making 
splices,  and  titles.  The  third  chapter  discusses  lenses,  artificial  lighting,  subjects 
for  photographing;  and  the  fourth  chapter  deals  with  fades,  multiple  exposures, 
irises,  and  dissolves.  The  last  chapter  explains  the  use  of  Kodacolor,  animation, 
close-ups,  and  various  other  applications  of  motion  pictures.  Finally,  a  few 
pages  are  devoted  to  the  purposes  and  aims  of  the  Amateur  Cinema  League. 






A.  N.  GOLDSMITH,  570  Lexington  Ave.,  New  York,  N.  Y. 

J.  I.  CRABTREE,  Eastman  Kodak  Company,  Rochester.  N.  Y. 


E.  I.  SPONABLE,  Fox  Film  Corp.,  New  York.  N.  Y. 
W.  C.  KUNZMANN,  National  Carbon  Co.,  Cleveland,  Ohio. 

J.  H.  KURLANDER,  Westhighouse  Lamp  Co.,   Bloomfield,  N.  J. 

H.  T.  COWLING,  Rochester,  N.  Y. 

Board  of  Governors 

H.  T.  COWLING,   311  Alexander  St.,  Rochester,  N.  Y. 

J.  I.  CRABTREE,  Research  Laboratories,  Eastman  Kodak  Co.,  Rochester,  N.  Y. 

P.  H.  EVANS,  Warner  Bros.  Pictures,  Inc.,  1277  E.  14th  St.,  Brooklyn,  N.  Y. 

R.  E.  FARNHAM,  General  Electric  Co.,  Nela  Park,  Cleveland,  Ohio. 

O.  M.  GLUNT,  Bell  Telephone  Laboratories,  Inc.,  New  York,  N.  Y. 

A.  N.  GOLDSMITH,  570  Lexington  Ave.,  New  York,  N.  Y. 

H.  GRIFFIN,  International  Projector  Corp.,  98  Gold  St.,  New  York,  N.  Y. 

W.  C.  HUBBARD,  General  Electric  Vapor  Lamp  Co.,  Hoboken,  N.  J. 

R.  F.  MITCHELL,  Bell  &  Howell  Co.,  1801  Larchmont  Ave.,  Chicago,  111. 

J.  H.  KURLANDER,  Westinghouse  Lamp  Co.,  Bloomfield,  N.  J. 

W.  C.  KUNZMANN,  National  Carbon  Co.,  Cleveland,  Ohio. 

E.  HUSE,  Eastman  Kodak  Co.,  6706  Santa  Monica  Ave.,  Hollywood,  Calif. 

E.  I.  SPONABLE,  Fox  Film  Corp.,  850  Tenth  Ave.,  New  York.  N.  Y. 







J.    H.    KURLANDER 






[j.  s.  M.  p.  E. 

O.  M.  GLUNT 




I          i 



Pacific  Coast  Section 

P.  H.  EVANS 

New  York  Section 


Chicago  Section 

Mar.,  1933] 



W.  V.  D.  KELLEY 


R.  M.  EVANS 

O.  B.  DEPUE 


B.  W.  DEPUE 

C.  D.  ELMS 

E.  R.  GEIB 


B.  W.  DEPUE 
O.  B.  DEPUE 




P.  D.  BREWSTER,  Chairman 
R.  M.  EVANS,  Vice-Chairman 


N.  M.  LA  PORTE 

W.  C.  KUNZMANN,  Chairman 


Development  and  Care  of  Film 
R.  F.  NICHOLSON,  Chairman 







C.  L.  GREGORY,  Chairman 
E.  THEISEN,  Vice- Chairman 


Membership  and  Subscription 

H.  T.  COWLING,  Chairman 
W.  H.  CARSON,  Vice-Chairman 

J.  G.  T.  GlLMOUR 

E.  E.  LAMB 

E.  THEISEN,  Chairman 

W.  V.  D.  KELLEY 



V.  B.  SEASE 
J.  H.  SPRAY 






[J.  S.  M.  P.  E. 

A.  A.  COOK 
W.  B.  COOK 
H.  A.  DEVRY 

Non-Theatrical  Equipment 
R.  E.  FARNHAM,  Chairman 

E.  R.  GEIB 
N.  B.  GREEN 
L.  A.  JONES 


R.  P.  MAY 



P.  H.  EVANS 
A.  C.  HARDY 


O.  M.  GLUNT,  Chairman 
G.  A.  CHAMBERS,  Vice-Chairman 

P.  A.  McGuiRE 
D.  McNicoL 

T.  E.  SHEA 


Preservation  of  Film 
W.  H.  CARSON,  Chairman 




V.  B.  SEASE 


A.  A.  COOK 


J.  G.  FRAYNE,  Chairman 

F.  S.  IRBY 
E.  E.  LAMB 

S.  S.  A.  WATKINS 

J.  O.  BAKER 
J.  J.  FINN 

Projection  Practice 

H.  RUBIN,  Chairman 



P.  A.  McGuiRE 



E.  R.  GEIB 

Projection  Screens 
S.  K.  WOLF,  Chairman 

A.  L.  RAVEN 


Mar.,  1933] 



H.  P.  GAGE 

Projection  Theory 
A.  C.  HARDY,  Chairman 


B.  W.  DEPUE 

W.  WHITMORE,  Chairman 


F.  S.  IRBY 


D.  McNicoL 

P.  H.  EVANS 
N.  M.  LA  PORTE 

H.  B.  SANTEE,  Chairman 


S.  K.  WOLF 

L.  E.  CLARK 
P.  H.  EVANS 
R.  M.  EVANS 

Standards  and  Nomenclature 
M.  C.  BATSEL,  Chairman 

A.  C.  HARDY 
L.  A.  JONES 
N.  M.  LA  PORTE 

V.  B.  SEASE 
T.  E.  SHEA 
S.  K.  WOLF 


Studio  Lighting 

P.  MOLE,  Chairman 


Chicago  Section 

R.  F.  MITCHELL,  Chairman  O.  B.  DEPUE,  Manager 

B.  W.  DEPUE,  Sec.-Treas.  J.  E.  JENKINS,  Manager 

New  York  Section 

P.  H.  EVANS,  Chairman  M.  C.  BATSEL,  Manager 

D.  E.  HYNDMAN,  Sec.-Treas.  J.  L.  SPENCE,  Manager 

Pacific  Coast  Section 

EMERY  HUSE,  Chairman  C.  DREHER,  Manager 

G.  F.  RACKETT,  Sec.-Treas.  J.  A.  DUBRAY,  Manager 




Arrangements  for  the  approaching  Spring,  1933,  Convention,  to  be  held  at  New 
York,  April  24  to  28,  with  headquarters  at  the  Hotel  Pennsylvania,  are  rapidly 
proceeding,  the  plans  including  a  number  of  outstanding  presentations  that  will 
make  it  worth  every  one's  while  to  be  present  at  the  meeting.  Standardization 
is  to  play  an  important  part  in  the  proceedings.  The  economy  trends  in  sound 
picture  production  and  exhibition  that  the  industry  is  now  showing  will  be 

The  semi-annual  banquet  of  the  Society  is  to  be  held  on  April  26,  at  the  Hotel 
Pennsylvania.  An  evening  of  pleasure  and  interest  is  promised,  and  all  are  urged 
to  make  every  effort  to  attend. 

Mr.  W.  C.  Kunzmann,  chairman  of  the  Convention  Committee,  is  being  ably 
assisted  in  his  efforts  to  make  the  Convention  an  outstanding  success  by  the 
Local  Arrangements  Committee  consisting  of: 

H.  GRIFFIN,  Chairman 





All  technical  sessions  will  be  held  in  the  Salle  Moderne,  on  the  roof  of  the  Hotel 
Pennsylvania.  Registration  will  be  opened  at  9  A.M.,  Monday,  April  24.  The 
registration  fee  will  be  $3,  and  the  banquet  charge  $4.50. 

Plans  are  being  made  to  assist  out-of-town  visitors  to  the  Convention  to  pass 
an  interesting  time  while  in  New  York,  and  special  film  programs  and  trips  of 
interest  will  be  arranged.  Full  details  of  the  program,  including  hotel  rates 
and  other  pertinent  information,  will  be  mailed  to  the  members  of  the  Society  at  a 
later  date.  Members  and  friends  of  the  Society  are  urged  to  make  every  effort  to 
attend  the  Convention. 


Arrangements  are  being  made  to  hold  an  exhibit  of  newly  developed  motion 
picture  apparatus,  in  order  to  acquaint  the  members  of  the  Society  with  the  newly 
devised  tools  of  the  industry.  This  exhibit  will  not  be  of  the  same  nature  as  the 
usual  trade  exhibit.  There  will  be  no  booths,  although  each  exhibit  will  be 
allotted  definite  space,  and  all  exhibits  will  be  arranged  in  one  large  room.  The 
following  regulations  will  apply: 


1.  The  apparatus  to  be  exhibited  should  be  new  or  have  been  developed  or 
improved  within  the  past  12  months. 

2.  Each  exhibitor  will  be  permitted  to  display  a  card  giving  the  name  of  the 
manufacturing  concern,  and  each  piece  of  equipment  shall  be  labeled  with  a 
plain  label  free  from  the  name  of  the  manufacturer. 

3.  A  technical  expert  capable  of  explaining  the  features  of  the  apparatus  ex- 
hibited must  be  present  during  the  period  of  the  exhibition. 

4.  A  charge  for  the  exhibit  will  be  made  in  accordance  with  the  space  occupied, 
as  follows:     up  to  20  sq.  ft.,  $10.00;    20  to  30  sq.  ft.,  $15.00;    30  to  40  sq.  ft., 
$20.00;  40  to  50  sq.  ft.,  $25.00. 

Please  direct  requests  for  space  to  the  General  Office  of  the  Society,  33  West 
42nd  St.,  New  York,  N.  Y.,  stating  the  number  and  nature  of  the  items  to  be 


At  a  meeting  held  on  January  27,  at  New  York,  plans  were  laid  for  the  papers 
program  of  the  approaching  Convention,  announced  above.  When  the  arrange- 
ments shall  have  been  completed,  copies  of  the  final  program  will  be  mailed, 
together  with  other  information  concerning  the  convention,  to  all  the  members 
of  the  Society.  The  plans  include  symposiums  on  the  economic  trends  in  the 
production  and  exhibition  of  motion  pictures  and  a  number  of  demonstrations 
of  remarkable  interest.  Among  the  later  will  be  the  presentation  to  the  Society, 
by  the  Projection  Practice  Committee,  of  the  test  film  described  in  Society 
Announcements  in  the  February  issue  of  the  JOURNAL. 

Mr.  O.  M.  Glunt,  chairman  of  the  Papers  Committee,  also  indicates  that  an 
interesting  session  will  be  devoted  to  the  subject  of  producing  special  types  of 
motion  pictures,  such  as  educational,  industrial,  animated  cartoons,  and  the  like. 
Considerable  attention  is  being  paid  also  to  subjects  of  direct  interest  to  exhibi- 
tors, and  it  is  expected  that  papers  dealing  with  these  subjects  will  be  presented 
by  a  group  of  men  prominent  in  the  field  of  exhibition. 


It  was  with  the  greatest  reluctance  that  the  Board  of  Governors,  meeting  on 
January  20,  1932,  at  the  Hotel  Sagamore,  Rochester,  N.  Y.,  resolved  to  accept  the 
resignation  of  Mr.  Lawrence  C.  Porter,  which  had  been  tendered  as  a  result  of 
his  entering  fields  of  activity  remote  from  the  motion  picture  industry. 

Mr.  Porter  was  one  of  the  charter  members  of  the  Society  and  served  uninter- 
ruptedly in  an  official  capacity  from  1921  to  date,  alternating  from  Governor  in 
1921,  President,  1922-23,  Past  President,  1924-25,  Governor,  1926,  Secretary, 
1927-28,  President,  1929,  Past  President,  1930-31,  Governor,  1932  to  date. 

Resolved:  That  the  Board  of  Governors  record  its  deep  appreciation  of  the  many 
years  of  faithful  and  unselfish  service  to  the  Society  rendered  by  Mr.  Porter.  Per- 
haps no  other  member  has  contributed  so  much  as  has  Mr.  Porter  to  the  upbuilding 
of  the  Society,  his  efforts  being  a  natural  result  of  his  unbounding  energy,  industry, 


integrity,  sound  judgment,  and  charming  personality.     The  loss  of  his  services  is 
deeply  regretted  by  every  member  of  the  Board ;  it  is  a  great  loss  to  the  Society. 


At  a  meeting  held  at  New  York,  N.  Y.,  on  February  3,  the  subject  of  standard- 
izing on  a  single  \ype  of  film  perforation  was  discussed,  in  view  of  difficulties  that 
seem  to  exist  owing  to  the  use  of  different  perforations  for  positive  and  negative 
film.  The  Committee  is  proceeding  to  investigate  the  elements  of  the  problem, 
and  will  report  on  them  at  the  forthcoming  convention,  to  whatever  extent  the 
intervening  time  permits. 

Other  matters  include  the  compiling  of  a  glossary  of  terms  used  in  color  cine- 
matography, work  on  which  is  now  proceeding  under  the  efforts  of  the  Color 
Committee,  and  the  desirability  of  arriving  at  some  form  of  standardization  in 
the  field  of  sensitometry  were  discussed. 

A  revision  of  the  present  booklet  of  standards  is  under  way,  which,  when  com- 
pleted, will  form  a  considerable  part  of  the  Committee's  report.  Other  subjects 
on  which  the  Committee  is  working  concern  the  standardization  of  sprocket  di- 
mensions, variations  in  the  width  of  reel  hubs,  and  the  possibility  of  standardizing 
the  sizes  of  projection  screens. 


On  January  9,  a  meeting  of  this  Committee,  held  at  New  York,  was  called  for 
the  purpose  of  organizing  the  work  and  outlining  the  plans  for  the  report  to  be 
rendered  at  the  Spring  Convention. 

Another  meeting  was  held  on  January  31,  at  which  time  the  subjects  previously 
outlined  were  discussed  in  greater  detail  and  the  framework  of  the  report  con- 
structed. Among  the  problems  facing  the  Committee,  at  the  present  time  are 
those  concerned  with  the  introduction  and  use  of  the  wider  range  of  frequency 
and  volume  in  recording  and  reproducing  sound.  Other  subjects  deal  with  the 
problems  of  film  development  and  auditorium  acoustics. 


The  Museum  Committee,  under  the  chairmanship  of  Mr.  E.  Theisen,  has 
been  fortunate  in  having  the  active  assistance  of  the  personnel  of  the  Los  Angeles 
Museum  during  the  past  few  months  in  improving  and  extending  the  S.  M.  P.  E. 
exhibit  at  that  museum.  New  accessions  to  the  exhibit  include  memoirs  of 
Vitagraph  by  J.  Stuart  Blackton,  and  an  additional  presentation  by  Mary  Pick- 
ford  and  Douglas  Fairbanks.  The  R.  K.  O.  Studios  have  made  for  the  exhibit 
a  series  of  devices  illustrating  the  methods  of  creating  artificial  rain,  wind,  rail- 
road, and  other  noises  to  be  synchronized  with  photographed  pictures.  There 
were  obtained  also  a  series  of  miniatures  made  by  Willis  O'Brien,  who  made  The 
Lost  World,  and  a  collection  of  manuscripts  written  by  Griffith,  Sennett,  Florence 
Lawrence,  King  Baggott,  and  about  fifty  others,  dating  from  about  1902  to  the 
present  time.  Some  of  these  are  only  six  scenes  long,  and  bear  itemized  expense 
accounts  of  less  than  a  hundred  dollars  recorded  in  pencil.  Many  small  accessions 
have  been  received,  too  numerous  to  mention,  and  a  considerable  amount  of  ma- 
terial has  been  promised. 

Mar.,  1933]  SOCIETY  ANNOUNCEMENTS  277 

The  chairman  of  the  Committee  is  making  available  for  the  students  of  the 
University  of  Southern  California  such  facilities  as  the  exhibit  may  command 
in  the  way  of  furnishing  information  for  theses  and  other  research  for  their  studies 
of  motion  picture  appreciation.  (This  University  is  the  first  to  raise  the  study  of 
motion  picture  dramaturgy  and  technic  to  the  academic  rating,  offering  college 
credits  for  the  courses.) 


At  a  meeting  held  at  New  York,  N.  Y.,  on  February  17,  consideration  was  given 
to  the  desirability,  and  possibility,  of  standardizing  the  sizes  of  projection  screens. 
Such  standardization,  the  Committee  felt,  would  eliminate  a  great  deal  of  waste, 
both  of  time  and  material,  for  which  the  patron  of  the  theater  must  eventually 
pay;  would  avoid  errors  in  ordering  screens;  would  expedite  the  shipment  of 
screens  when  so  ordered,  and  lead  to  lower  costs. 

It  was  the  general  opinion  of  the  Committee  that  the  sizes  of  screen  should  be 
specified  in  terms  of  the  size  of  the  picture,  the  specification  referring  only  to  the 
width  of  the  picture  because  of  the  invariable  relation  (0.600  X  0.825)  between 
the  width  and  height;  thus,  a  No.  20  screen  would  refer  to  a  picture  area  20  feet 
wide  and  14.5  feet  high. 

The  Committee  also  considered  the  relation  between  the  width  of  the  screen 
and  the  distance  of  the  front  row  of  seats  from  the  screen,  as  well  as  the  maximum 
angle  at  which  the  screen  should  be  viewed  in  order  to  avoid  excessive  fore- 
shortening of  the  picture.  In  addition,  plans  were  discussed  for  supplying,  as 
part  of  the  Committee's  report,  samples  of  paper  chosen  according  to  their 
reflectivities,  which,  when  viewed  against  the  screens  by  the  exhibitor,  would 
furnish  an  approximation  to  the  reflectivity  of  his  screen  on  choosing  the  paper 
sample  that  most  nearly  matched  the  screen  in  respect  to  brightness. 

These  subjects  will  be  discussed  in  detail  in  the  report  of  the  Committee,  to  be 
presented  at  the  Spring  Meeting  at  New  York,  April  24  to  28. 


This  Committee  consists  of  representatives  of  the  several  projection  committees, 
who  have  been  meeting  recently  for  the  purpose  of  looking  more  carefully,  and 
from  all  points  of  view,  into  the  problem  of  determining  what  screen  characteristics 
are  found  in  the  field,  and  what  recommendations  to  the  field  might  be  advisable, 
both  in  respect  to  the  screen  brightness  itself  and  to  methods  of  measuring  it. 
The  Committee  consists  of  Mr.  S.  K.  Wolf,  chairman  of  the  Projection  Screens 
Committee;  Prof.  A.  C.  Hardy,  chairman  of  the  Projection  Theory  Committee; 
Mr.  H.  Rubin,  chairman  of  the  Projection  Practice  Committee;  and  Mr.  W.  F. 
Little;  who  have  been  assisted  at  their  meetings  by«Mr.  McCandless,  of  the 
Illuminating  Engineering  Society. 


At  a  meeting  held  on  February  15  at  the  General  Office  of  the  Society,  the  final 
form  of  the  report  of  the  sub-committee,  published  in  this  issue  of  the  JOURNAL, 
was  determined.  In  addition,  plans  were  laid  for  the  more  detailed  examination 


of  some  of  the  subjects  mentioned  in  the  report,  with  the  view  of  arriving  at 
definite  recommendations  for  the  conduct  of  exchange  work  that  might  form  the 
basis  of  subsequent  reports.  The  present  agenda  call  for  a  study  of  film  season- 
ing, the  character  of  damage  done  to  film  outside  the  exchanges,  splicing  of  film, 
and  dimensions  of  reels. 


Instead  of  holding  the  usual  form  of  meeting  this  month,  the  members  of  the 
New  York  Section  were  given  the  opportunity  of  inspecting  the  new  installations 
at  the  Radio  City  Music  Hall  on  the  morning  of  February  12.  The  tour  through 
the  building  was  led  by  Mr.  R.  Cox,  of  the  sound  department  of  RKO  Theaters, 
who  briefly  described  the  equipment  of  the  projection  rooms  and  the  general  stage 
and  theater  equipment,  including  the  lifts,  the  lighting,  etc.  The  tour  covered 
the  entire  theater,  the  lounges,  lobbies,  cafeteria,  etc.  Thanks  are  due  the  RKO 
management  for  the  privilege  accorded  the  members  of  the  Section. 


Bausch  &  Lomb  Optical  Co. 
Bell  Telephone  Laboratories 
Burnett-Timken  Laboratories 

Eastman  Kodak  Co. 
Electrical  Research  Products,  Inc. 

National  Carbon  Co. 

RCA  Victor  Co.,  Inc. 




By  action  of  the  Board  of  Governors,  October  4,  1931,  this  Honor  Roll  was  estab- 
lished for  the  purpose  of  perpetuating  the  names  of  distinguished  pioneers  who  are 
now  deceased: 




Copies  of  the  publications  listed  here  may  be  obtained  free  of  charge  by  addressing 
a  request  to  the  manufacturer  named.  Manufacturers  are  requested  to  send  new 
publications  to  the  General  Office  of  the  Society  immediately  upon  issue. 

Bell  &  Howell  Co.:  Bulletin  describing  a  new  Character  Title  Writer,  to  be 
used  with  Filmo  Cameras;  the  unit  can  be  used  for  making  movable-letter  ani- 
mated titles,  the  Title  Writer  being  used  vertically  so  that  it  is  not  necessary  to 
fasten  the  letters  to  the  card.  For  ordinary  titles  showing  the  hand  as  it  writes, 
the  unit  is  set  up  horizontally  or  at  an  angle  to  the  table- top.  Two  100- watt, 
11 5- volt  lamps  are  used,  the  lamps  being  silvered  on  one  side  so  as  to  avoid  the 
need  of  reflectors.  They  are  mounted  on  joint  and  swivel  supports  so  as  to  permit 
their  proper  adjustment  for  avoiding  reflection  into  the  camera  from  glossy 
subjects  and  to  permit  shadow  effects  to  be  obtained.  Address:  1801  Larch- 
mont  Ave.,  Chicago,  111. 

Du  Pont  Film  Mfg.  Corp.*  Bulletin  NF-2,  describing  du  Pont  dupac negative. 
This  is  a  bi-pack  combination  of  two  special  negatives  to  be  used  in  standard 
cameras,  for  making  two-color  separation  negatives.  Only  a  moderate  initial 
outlay  is  necessary  for  making  the  necessary  camera  changes  and  special  maga- 
zine equipment.  It  is  stated  that  the  means  employed  in  the  front  negative  for 
filtering  the  light  make  it  possible  to  retain  the  full  working  speed  and  contrast 
of  the  front  film  emulsion,  and  at  the  same  time  to  filter  accurately  and  uni- 
formly the  light  passing  through  to  the  rear  negative.  It  is  also  said  to  be  possible 
to  hypersensitize  the  negative  and  to  process  it  without  contaminating  the  solu- 
tions with  dyes.  Address:  Parlin,  N.  J. 

The  Educational  Screen,  Inc.:  A  booklet  entitled  1000  and  One,  The  Blue 
Book  of  Non-Theatrical  Films.  A  classified  list  of  the  films  obtainable  in  a  great 
many  subjects.  Full  information  is  given  concerning  the  title,  number  of  reels, 
nature  of  the  subject,  and  distributor,  for  16-mm.  silent,  16-mm.  sound-on-disk, 
35-mm.  silent,  and  35-mm.  sound-on-film  or  disk.  The  subjects  embrace  most 
phases  of  science,  sociology,  government,  health  and  hygiene,  industry  and 
engineering,  literature  and  drama,  psychology,  war — naval  and  military.  Re- 
ligion, comedy,  and  travel  subjects  are  included.  Address:  64  E.  Lake  St., 
Chicago,  111. 

General  Radio  Co.:  Catalogue  G,  lists  and  describes  the  construction  and  uses 
of  electrical  measuring  apparatus  and  accessories  such  as  resistance  devices, 
condensers,  inductors,  frequency  and  time  measuring  devices,  oscillators  and 
amplifiers,  bridges,  generators,  instruments  for  measuring  modulation  and  dis- 
tortion, oscillographs,  etc.  Address:  Cambridge  A,  Mass. 

General  Radio  Co.:  The  General  Radio  Experimenter,  Vol.  vii,  No.  7,  de- 
scribes the  principles  and  applications  of  the  stroboscope  in  studying  the  motions 
of  objects;  the  elementary  mathematical  theory  of  the  stroboscope  is  also  pre- 
sented briefly.  The  Edgerton  Stroboscope  (type  548- A)  employs  a  high-intensity 



mercury  arc,  the  flash  of  which  has  a  duration  of  only  five  microseconds,  during 
which  interval  an  object  moving  at  the  rate  of  a  mile  a  minute  traverses  a  dis- 
tance of  only  five-thousandths  of  an  inch.  Fundamental  synchronism  can  be 
achieved  at  rotational  speeds  up  to  10,000  r.p.m.  Address:  Cambridge  A, 

Globe  Automatic  Sprinkler  Co.:  Bulletins  describing  the  model  C  Dry  Pipe 
valve  and  the  Saveall  Airomatic  Sprinkler  System.  Details  are  given  of  the  con- 
struction and  design  features  of  the  equipment,  and  the  manner  of  making  the 
installations.  The  Saveall  Sprinkler  System  is  designed  particularly  for  installa- 
tions where  the  supply  of  water  is  limited  and  where  the  Standard  Automatic 
sprinkler  systems  may  not  be  used  economically.  Address:  2035  Washington 
Ave.,  Philadelphia,  Pa. 

Jenkins  &  Adair,  Inc. :  Circular  describing  the  Phonopticon  and  Contr otophone. 
These  are  sound-on-disk  reproducing  devices,  for  which  special  disks  are  prepared 
having  recorded  on  them  sub-audible  (50  cycle)  notes,  lasting  but  a  brief  interval 
and  recorded  at  selected  points  in  the  sequence  or  scenario.  The  50-cycle  note, 
upon  actuating  the  pick-up,  is  diverted  from  the  reproducing  amplifier  by  means 
of  a  selective  filter,  and  is  made  to  operate  a  relay.  In  the  Phonopticon  the  relay 
is  made  to  open  and  close  the  circuits  of  a  motor  driven  mechanism  for  changing 
lantern  slides  at  the  instants  when  the  50-cycle  notes  occur  on  the  disk.  The 
Controlophone  is  a  special  adaptation  of  such  a  system  for  sales  promotional  and 
educational  purposes.  Both  types  of  instruments  are  mounted  in  suitable  cabi- 
nets, and  may  be  used  for  presenting  lectures,  travelogues,  sales  talks,  etc.  Ad- 
dress: 3333  Belmont  Ave.,  Chicago,  111. 

RCA  Victor  Co.:  A  booklet  describing  the  new  RCA  Victor  sound  recording 
system  having  the  features  of  increased  dynamic  range,  increased  frequency  range, 
and  decreased  ground  noise.  The  applications  of  the  system  to  the  needs  of 
motion  picture  theaters  are  described,  and  a  general  description  of  the  principles 
of  the  system  is  presented.  The  various  design  and  construction  features  of  the 
component  parts  of  the  equipment  are  described  in  detail. 

Victor  Animatograph  Corp.:  This  circular  announces  a  new  500- watt  Mazda 
lamp,  produced  by  the  General  Electric  National  Lamp  Works,  which  is  suitable 
for  use  in  the  Victor  Model  10FH  Premier  Hi-Power  16-mm.  projector.  Al- 
though this  projector,  having  a  built-in  lamp  resistor  in  the  base,  is  ordinarily 
supplied  with  the  400- watt  lamp,  it  will  accommodate  the  new  lamp  without  altera- 
tions of  any  kind.  The  500-watt  lamp  is  supplied  only  when  so  specified.  It 
operates  at  100  volts,  and  should  not  be  confused  with  the  older  T12  500-watt, 
110-120- volt  lamp.  The  new  lamp  employs  an  8-coil  biplanar  filament,  and 
provides  greater  illumination.  Address:  Davenport,  Iowa. 




Volume  XX  APRIL,  1933  Number  4 


Composite  Photographic  Processes H.  D.  HINELINE     283 

The  Optical-Photographic  Principles  of  the  Agfacolor  Process. 

F.  WEIL    301 

The  Production  of  Animated  Cartoons W.  GARITY    309 

A  Method  of  Measuring  Axial  Chromatic  Aberration  in  an 
Objective  Lens W.  HERRIOTT  323 

A  New  Way  of  Splitting  Seconds C.  H.  FETTER    332 

A  Method  for  the  Calculation  of  the  Correct  and  Most  Eco- 
nomical Concentrations  of  Elon  and  Hydroquinone  in  a 
Borax  Developer  for  Motion  Picture  Film 

A.    M.    GUNDELFINGER      343 

Officers 355 

Society  Announcements 356 





Board  of  Editors 

J.  I.  CRABTREE,  Chairman 



Published  monthly  at  Easton,  Pa.,  by  the  Society  of  Motion  Picture  Engineers. 

Publication  Office,  20th  &  Northampton  Sts.,  Easton,  Pa. 
General  and  Editorial  Office,  33  West  42nd  St.,  New  York,  N.  Y. 

Copyrighted,  1933,  by  the  Society  of  Motion  Picture  Engineers,  Inc. 

Subscription  to  non-members,  $12.00  per  annum;  to  members,  $9.00  per  annum, 
included  in  their  annual  membership  dues;  single  copies,  $1.50.  A  discount 
on  subscriptions  or  single  copies  of  15  per  cent  is  allowed  to  accredited  agencies. 
Order  from  the  Society  of  Motion  Picture  Engineers,  Inc.,  20th  and  Northampton 
Sts.,  Easton,  Pa.,  or  33  W.  42nd  St.,  New  York,  N.  Y. 

Papers  appearing  in  this  Journal  may  be  reprinted,  abstracted,  or  abridged 
provided  credit  is  given  to  the  Journal  of  the  Society  of  Motion  Picture  Engineers 
and  to  the  author,  or  authors,  of  the  papers  in  question.  The  Society  is  not  re- 
sponsible for  statements  made  by  authors . 

Entered  as  second  class  matter  January  15,  1930,  at  the  Post  Office  at  Easton, 
Pa.,  under  the  Act  of  March  3,  1879. 


Summary. — The  author  traces  in  this  paper  the  development  of  composite  photo- 
graphic processes,  in  terms  of  the  patent  history  of  the  art,  from  its  beginning  to  April 
1,  1932.  For  convenience,  the  art  is  divided  into  three  phases,  namely:  the  mask 
process,  the  projection  process,  and  the  color-separation  process.  Each  of  these  lines 
has  evolved  into  several  variants,  the  development  of  which  is  traced  through  the  patent 

Composite  photography  may  be  described  as  the  process  of  making 
pictures  in  which  the  background  and  the  foreground  are  obtained 
from  separate  sources,  and  combined  to  produce  the  completed 
picture.  To  obtain  a  satisfactory  combination,  some  means  must 
obviously  be  provided  to  prevent  overlapping  of  the  respective 
picture-element  images.  Various  means  have  been  proposed  and 
described  chronologically  in  various  United  States  patents,  which 
form  the  original  sources  of  material  for  the  following  descrip- 
tion of  the  suggested  processes. 

The  patent  literature  describes  three  kinds  of  processes,  which 
differ  broadly  in  their  various  details.  The  earliest  process  in  point 
of  time  may  be  called  the  mask  process;  the  next  may  be  called  the 
projection  process;  and  the  third  may  be  called  the  color-separation 
process.  The  mask  process  has  developed  along  several  lines, 
yielding  a  number  of  variants  that  differ  considerably  among  them- 
selves, although  all  utilize  some  kind  of  opaque  mask  or  shield  for 
separating  the  components  of  the  picture  and  for  avoiding  such 
difficulties  as  overlapping,  "ride,"  ghosting,  and  fringing.  Also, 
certain  of  the  suggested  processes  utilize  elements  of  all  three  of  the 
processes  as  hereinafter  differentiated. 

As  is  usual  in  commercial  photographic  work,  comparatively  little 
information  has  been  published,  either  in  the  technical  or  popular 

*  Received  March  7,  1932. 
**  Patent  Solicitor,  New  York,  N.  Y. 


284  H.  D.  HINELINE  [J.  S.  M.  P.  E. 

journals,  bearing  on  these  composite  processes,  and  the  most  detailed 
information  seems  to  be  found  in  the  patented  art. 


The  first  patent  publication  of  a  composite  photographic  process 
was  patent  No.  149,724,  issued  on  April  14,  1874,  to  C.  M.  Coolidge. 
This  patent  describes,  of  course,  only  a  still  photographic  process, 
as  it  was  issued  long  before  the  days  of  motion  pictures.  But  the 
principle  of  holding  a  card,  screen,  or  mask,  carrying  the  desired  fore- 
ground matter,  in  front  of  undesired  parts  of  the  subject  in  order  to 
achieve  a  cartoon  effect,  is  the  forerunner  of  many  of  the  later 
processes,  and  carries  the  germ  of  the  idea  from  which  the  later- 
developed  mask,  screen,  and  cartoon  processes  grew. 

During  the  twenty  years  following  the  issuance  of  this  patent, 
the  foundation  was  laid  for  all  the  other  types  of  composite  processes, 
as  will  later  be  described;  the  patents  that  were  published  related, 
mostly,  or  at  first,  to  still  photography  only,  later  branching  out  into 
the  motion  picture  art  soon  after  the  advent  of  the  screen.  For  some 
reason  effort  seems  to  have  been  concentrated  for  a  time  on  the 
processes  other  than  the  mask  process,  with  the  result  that  we  do 
not  find  another  patent  for  a  screen  or  mask  process  until  October 
19,  1915,  when  patent  No.  1,156,896  was  issued  to  J.  E.  Garrette. 
Nevertheless,  much  more  work  seems  to  have  been  done  on  the  mask 
and  screen  processes  than  on  all  the  other  processes,  if  one  may  judge 
by  the  number  of  patents  that  were  issued. 

The  Garrette  patent  describes  the  use  of  a  combination  of  colored 
lantern-slide  and  motion  picture  film  for  simultaneous  projection, 
the  slide  having  a  portion  prepared  to  be  occupied  by  the  small  field 
of  the  moving  picture.  The  stationary  slide  thus  becomes,  in  effect, 
a  screen  or  mask  cooperating  with  the  motion  picture,  and  is  claimed 
so  to  act  in  the  patent,  which  also  contains  claims  referring  to  the 
projector.  The  patent  has,  however,  expired. 

The  first  mention  of  the  device  that  may  be  called  a  traveling  mask 
is  found  in  patent  No.  1,226,135,  issued  on  May  15,  1917,  to  R.  V. 
Stambaugh.  In  this  patent  is  disclosed  a  motion  picture  negative, 
which  may  be  a  cartoon  if  desired,  having  a  clear  space  in  each  frame. 
This  negative,  which  may  be  regarded  as  the  traveling  mask,  is  placed 
in  the  camera  together  with  an  unexposed  film,  the  camera  then 
being  trained  on  a  card  bearing  the  matter  to  be  added  to  the  first 
negative.  The  light  from  the  white  portions  of  the  card  prints  the 


negative,  while  the  lettering  or  other  matter  on  the  card  is  photo- 
graphed directly  on  the  unexposed  film  through  the  clear  portion 
of  the  negative.  The  object  of  the  process  is  to  produce  a  number  of 
advertising  films,  respectively  carrying  the  names  of  different  ad- 
vertisers, and  different  cop/,  but  using  only  a  single  negative  of  the 
action  or  cartoon.  The  process  is  aimed  at  reducing  the  cost  of 
advertising  films.  It  may  be  of  interest  to  note  that  while  the 
patent  monopoly  has  yet  to  remain  in  force  about  two  more  years, 
the  claims  are  very  restricted,  being  limited  to  the  process  of  com- 
bination printing  of  a  negative  and  photographing  of  other  matter. 
As  this  is  the  actual  invention,  the  claims  are  properly  limited  to 
such  a  scope. 

The  next  patent,  chronologically,  applies  the  idea  of  the  Coolidge 
patent  to  the  making  of  animated  cartoons.  This  is  patent  No. 
1,261,648,  issued  April  2,  1918,  to  P.  H.  Terry.  It  teaches  a  method 
of  making  animated  cartoons  by  sketching  the  stationary  parts  of 
the  picture  upon  a  card  that  is  blackened  where  the  action  or  figures 
are  to  be,  the  figures  and  action  being  sketched  upon  another  series 
of  cards,  blackened  where  the  background  is  to  be.  Each  frame  of 
the  film  is  then  made  by  a  double  exposure,  using  the  background 
sketch  and  the  action  mask  for  one  exposure,  and  the  action 
sketch  and  background  mask  for  the  other  exposure.  The  claims 
are  based  on  the  superposition  of  successive  exposures,  and  ac- 
cordingly are  rather  limited  in  scope. 

The  first  mention  of  a  fixed  mask  used  inside  the  camera  is  found 
in  patent  No.  1,269,061,  issued  June  11,  1918,  to  Norman  Dawn. 
In  the  process  disclosed  photographs  are  made  of  the  foreground  and 
action  behind  a  vignette  or  screen  placed  inside  the  camera  so  as  to 
leave  the  top  and  background  portions  of  each  frame  unexposed. 
The  background  is  then  added  by  photographing  a  card  or  drawing 
of  the  desired  scene,  the  foreground  of  which  has  been  rendered  non- 
actinic.  The  claims  are  few  and  narrow  in  scope. 

The  complete  disclosure  of  the  process  using  a  traveling  mask  as 
now  known  is  first  found  in  patent  No.  1,273,435,  issued  July  23, 
1918,  to  F.  D.  Williams.  In  this  process,  the  action  is  photographed 
against  a  black  background,  yielding  a  negative  that  is  transparent 
except  for  the  action.  A  print  of  this  negative  is  then  made  in  such 
a  way  that  the  area  of  the  action  is  left  transparent,  the  background 
area  being  made  opaque  and  as  dense  as  possible  by  intensification. 
The  print  thus  produced  is  the  first  mask.  A  print  is  then  made 

286  H.  D.  HlNELINE  [J.  S.  M.  P.  E. 

from  this  mask,  producing  the  second  or  reverse  mask.  The  action 
negative  and  the  first  mask  are  placed  over  the  raw  film  and  printed; 
then  the  background  negative  and  the  second  mask  are  substituted 
and  the  raw  film  is  printed  again.  The  first  exposure  of  the  action 
is  protected  by  the  mask,  the  area  of  the  background  being  protected 
from  fogging  by  the  first  mask  during  the  first  printing.  The  dis- 
closure suggests  also  that  the  first  and  second  printing  may  be  both 
of  action,  as  a  duplication  of  a  single  actor.  The  claims  of  the 
patent  are  rather  broadly  drawn  to  the  double  masking  features  of 
the  invention. 

A  very  poorly  prepared  patent,  No.  1,279,099,  issued  September 
17,  1918,  to  C.  A.  Gilbert,  attempts  to  describe  a  process  of  com- 
bining with  a  drawn  background  a  photographed  silhouette  of  the 
action,  and  makes  such  claims;  but  the  description  is  more  sug- 
gestive than  detailed,  as  most  of  the  photographic  steps,  which  seem 
to  be  important,  are  left  to  the  imagination  of  the  reader. 

An  interesting,  but  perhaps  somewhat  impracticable  variant, 
which  suggests  but  probably  is  not  quite  a  traveling  mask,  is  found 
in  patent  No.  1,296,471,  issued  March  4,  1919,  to  L.  S.  Brainerd. 
The  system  disclosed  consists  of  a  camera,  in  front  of  which  is  posi- 
tioned a  guide  and  a  means  for  producing  intermittent  motion  of  a 
member  carrying  a  series  of  sketches  forming  the  successive  views  of 
an  animated  cartoon.  Beyond  the  strip,  in  the  same  field  of  view, 
there  is  also  provided  a  stage  for  action  by  ordinary  actors.  The 
actors  on  the  stage  and  the  cartoon  on  the  strip  are  then  combined 
on  a  single  film ;  but  it  does  not  affirmatively  appear  that  the  cartoon 
strip  is  transparent,  as  would  be  necessary  for  a  real  traveling  mask. 
The  claims  are  narrowly  drawn  to  the  combination  of  cartoon  and 

The  double  mask  system  of  the  Williams  patent  is  extended  to 
animated  cartoons,  made  from  life,  in  patent  No.  1,355,648,  issued 
October  12,  1920,  to  L.  E.  Brownley.  The  complementary  masks 
are,  however,  made  manually  rather  than  photographically,  so  as  to 
permit  the  desired  modification  of  the  outlines  of  the  characters. 
The  claims  are,  of  course,  restricted  in  scope  by  the  previous 
appearance  of  the  Williams  patent. 

A  better  disclosure  of  a  process  for  making  cartoons  by  using  a 
double  set  of  traveling  masks  is  found  in  patent  No.  1,375,918,  issued 
April  26,  1921,  to  C.  F.  Lederer.  In  this  patent  the  process  described 
requires  that  silhouettes  corresponding  to  the  outlines  of  the  action 


or  foreground  matter,  as  well  as  drawings  of  the  action,  be  made 
manually.  A  single  drawing  of  the  background  is  then  photographed 
through  the  appropriate  mask,  and  the  successive  drawings  of  the 
action  are  photographed  on  the  same  film  and  frame  through  the 
other  mask.  The  patent  contains  a  considerable  number  of  claims, 
not  very  broad,  but  covering  the  invention  well. 

Movement  of  a  simple  mask  crosswise  within  the  camera  is  dis- 
closed in  patent  No.  1,397,602,  issued  to  W.  O.  Owen,  on  November 
22,  1921.  This  seems  to  be  a  minor  matter,  but  the  issue  of  the 
patent  may  be  noted. 

An  interesting  variant  of  the  fixed  mask  idea  is  seen  in  patent 
No.  1,464,054,  issued  on  August  7,  1923,  to  F.  D.  Williams.  The 
desired  negative  of  the  action  is  printed  on  the  positive  stock,  in  a 
camera  which  is  used  as  a  printer  and  which  takes  both  the  negative 
and  the  raw  film  stock,  by  light  reflected  through  the  camera  lens 
from  a  card,  the  reflective  power  of  which  is  modified  so  that  light  is 
reflected  only  to  the  parts  of  the  negative  film  to  be  printed.  Supple- 
mentary cards  may  be  used  to  produce  a  composite,  or  double,  ex- 
posure so  as  to  combine  separately  photographed  foreground  and 

Another  patent,  disclosing  a  process  of  somewhat  doubtful  utility 
is  No.  1,476,885,  issued  December  11,  1923,  to  D.  W.  Griffith,  in 
which  a  screen  having  an  opening  is  used  as  an  intermediate  ground, 
with  the  foreground  action  in  front,  and  the  opening  closed.  After 
photographing  the  action  the  film  is  run  back  in  the  camera,  the 
screen  opening  is  cleared,  and  a  sketch  behind  the  opening  is  illumi- 
nated and  photographed.  The  reason  for  the  sequential,  rather  than 
simultaneous,  photographing  of  the  two  does  not  appear. 

An  interesting  but  somewhat  doubtful  variation  of  the  traveling 
mask  method  is  disclosed  in  patent  No.  1,503,731,  issued  August  5, 
1924,  to  J.  B.  Walker.  In  this  system  two  simultaneous  negative 
exposures  of  the  foreground  and  action  are  made;  one  of  these  is 
developed  and  used  to  make  a  printing  strip  for  relief  type;  ink  or 
dye  is  applied  to  the  other  negative  exposure,  as  yet  undeveloped, 
to  protect  the  foreground  while  the  background  exposure  is  being 
added.  Questions  may  be  raised  as  regards  the  shrinkage  of  the  film 
and  the  registration. 

Patent  No.  1,508,509,  issued  September  16,  1924,  to  L.  F.  Douglass, 
contains  some  interesting  claims  relating  to  the  use  of  supplementary 
masks  in  the  printer  for  combining  foreground  and  background. 

288  H.  D.  HINELINE  [j.  S.  M.  P.  E. 

A  similar  structure  in  the  taking  camera  is  shown  in  patent  No. 
1,543,065,  issued  June  23,  1925,  also  to  L.  F.  Douglass. 

A  convenient  method  of  making  complicated  masks  to  be  used  in 
the  camera  is  shown  in  patent  No.  1,572,315,  issued  February  9, 
1926,  to  E.  Scholl.  In  this  method  a  metal  strip  is  coated  with 
emulsion,  the  desired  background  scene  is  photographed  on  the 
strip,  the  desired  solid  portions  being  protected  by  resist  and  the  etch- 
ing being  done  through  the  desired  openings. 

Still  another  variant  of  the  early  Coolidge  patent  is  described  in 
patent  No.  1,574,464,  issued  February  23,  1926,  to  J.  Bartholowsky, 
disclosing  a  photographic  system  in  which  a  miniature  model  of  part 
of  the  background  is  placed  near  the  camera,  while  other  portions 
of  the  desired  scene,  of  full  size  and  visible  through  openings  in  the 
miniature,  are  placed  farther  away.  The  claims  seem  to  be  limited 
to  the  use  of  a  miniature  above  a  reference  level. 

Stationary  supplemental  masks  placed  outside  the  camera  are  dis- 
closed in  patent  No.  1,576,854,  issued  March  16,  1926,  to  J.  F.  Seitz. 
These  masks  are  used  with  a  rigid  frame  and  track  which  holds  the 
camera  and  mask  in  fixed  alignment.  The  masks  are  made  by  pro- 
jecting a  photograph  from  and  in  the  same  camera.  This  patent 
has  been  reissued  as  No.  Re  17,125. 

Patent  No.  1,589,731,  issued  June  22,  1926,  to  F.  D.  Williams, 
makes  a  somewhat  uncertain  attempt  at  disclosing  a  composite  proc- 
ess in  which  the  action  and  lower  portion  of  the  background  are 
photographed,  printed,  and  projected  to  a  screen,  a  sketch  of  the 
remainder  of  the  background  being  made  on  the  screen  which  is  then 
photographed  and  combined  with  the  foreground  and  action  in  ways 
not  clearly  described.  This  patent  also  has  been  reissued,  as  No. 
Re  17,330. 

In  using  traveling  mask  processes,  the  most  serious  technical  prob- 
lem is  that  of  registering  the  mask  accurately  with  the  various  nega- 
tives and  the  print  film,  in  view  of  the  differences  of  shrinkage  among 
the  various  films.  The  first  disclosure  of  means  designed  to  avoid 
this  difficulty  appears  in  patent  No.  1,610,410,  issued  December  14, 
1926,  to  F.  F.  Baker.  Arrangements  are  made  for  splitting  the  light 
so  as  to  be  able  to  expose  the  action  negative  and  the  mask  film 
simultaneously,  and  suitable  means  are  provided  in  processing  for 
equalizing  the  shrinkage.  The  mask  film  is  then  used  in  photograph- 
ing the  background.  The  developed  foreground  and  background 
negatives  are  then  cemented  together,  and  printed  in  an  optical  printer. 


Patent  No.  1,616,237,  issued  February  1,  1927,  to  J.  F.  Seitz, 
is  a  companion  patent  to  the  previously  mentioned  patent  No. 
1,576,854.  Minor  modifications  of  the  system  are  described,  in 
which  an  enlargement  is  used  as  a  mask,  part  of  the  enlargement 
being  cut  away  so  as  to  permit  the  use  of  ordinary  stage  and  actors 
at  a  greater  distance. 

An  excellent  description  of  the  traveling  mask  process,  and  its 
application  to  the  two-color  subtractive  process  known  as  "Techni- 
color," is  given  in  patent  No.  1,641,566,  issued  September  6,  1927, 
to  J.  A.  Ball.  The  claims  are  directed  toward  two-color  compositing, 
but  the  description  shows  the  features  involved  in  obtaining  register 
in  the  traveling  mask  process,  and  also  means  for  obtaining  color 
balance  in  the  composite  film.  In  the  process  as  described  the  fore- 
ground and  background  are  combined  by  processing  the  color-separa- 
tion silver  print  images  in  combination  with  the  masks,  before  the 
color  printing  is  done,  compositing  being  done  separately  for  each 

The  extent  to  which  masks  may  be  used  outside  the  camera  is 
shown  in  patent  No.  1,669,963,  issued  May  15,  1928,  to  P.  W.  Young- 
blood.  The  process  requires  an  enlargement  of  the  desired  back- 
ground scene,  with  a  part  cut  out  where  the  action  is  to  occur.  The 
cut-out  opening  is  then  backed  by  a  larger  or  full-scale  enlargement, 
at  a  greater  distance  from  the  camera,  the  actors  performing  in  the 
space  between  the  two  enlargements.  The  patent  has  only  a  single, 
very  narrow  claim. 

An  interesting  means  of  obtaining  the  traveling  mask  is  shown  in 
patent  No.  1,697,315,  issued  January  1,  1929,  to  M.  Handschiegl. 
The  foreground  exposure  is  made  upon  a  film  that  is  not  color-sensi- 
tive, before  a  non-actinic  screen.  The  film  is  then  developed,  rinsed, 
and  dried  without  being  fixed,  and  the  mask  is  made  on  panchromatic 
film  by  exposing  it  to  light  to  which  the  first  film  is  not  sensitive,  such 
as  red  light.  The  background  exposure  may  then  be  added  to  the 
first  film,  using  the  mask  to  protect  the  foreground  exposure.  The 
film  is  then  developed  a  second  time,  fixed,  etc.,  yielding  the  desired 
composite  negative. 

A  traveling  mask  substitute  is  suggested  by  N.  Osann  in  patent 
No.  1,698,448,  issued  January  8,  1929.  The  exposure  of  the  fore- 
ground is  made  against  a  non-actinic  field,  and  developed.  Then, 
without  fixing  it,  the  developed  image  is  toned,  to  render  it  opaque; 
and  the  dried  film  is  reexposed  to  the  desired  background ;  it  is  again 

290  H.  D.  HlNELINE  [J.  S.  M.  P.  E. 

developed,  fixed,  etc.,  after  which  it  is  printed.  Although  this 
process  avoids  problems  of  registration,  it  substitutes  those  of  obtain- 
ing tone  balance,  and  introduces  chemical  and  grain  difficulties. 

An  elaborate  description  of  a  simple  double  exposure  process  is 
found  in  patent  No.  1,737,021,  issued  November  26,  1929,  to  G.  B. 
Pollock.  A  test  portion  of  the  'original  partly  exposed  action  film 
is  used  with  a  chart  board  to  aid  in  preparing  a  sketch  of  the  sub- 
stitute background.  It  does  not  appear  that  by  this  process  a  whole 
new  background  will  be  supplied,  but  that  only  a  portion  of  the  back- 
ground, separated  from  the  action,  will  be  replaced. 

An  odd  suggestion  is  made  in  patent  No.  1,771,029,  issued  July  22, 
1930,  to  J.  Burkhardt.  Successive  frames  carry  the  action  and  the 
background  alternately,  the  background  frames  having  opaque  por- 
tions corresponding  to  the  action  as  shown  in  the  adjacent  frames. 
The  adjacent  frames  are  then  projected  together,  for  the  effect  of 
relief,  seemingly  a  pseudo -stereoscopic  effect.  A  modification  in 
which  the  frames  are  placed  side  by  side,  instead  of  in  sequence,  is 
shown  in  patent  No.  1,785,336,  issued  December  16,  1930,  and  yet 
another  in  patent  No.  1,801,656,  issued  April  21,  1931. 

R.  J.  Pomeroy  discloses,  in  patent  No.  1,818,354,  issued  August 
11,  1931,  the  use  of  a  half -silvered  mirror  and  two  cameras,  one  camera 
making  the  action  negative,  and  the  other  making  the  mask,  using  a 
fuller  exposure  on  very  coiitrasty  working  stock.  The  mask  film 
is  then  developed,  etc.,  and  used  as  a  protection  for  the  action 
exposure  on  the  other  film  during  the  exposure  of  the  back- 

A  process  in  which  some  of  the  steps  of  the  animated  cartoon  proc- 
esses are  used  is  shown  by  O.  Chouinard,  in  patent  No.  1,827,282, 
issued  October  13,  1931.  In  this  process  two  similar  negatives  are 
made  simultaneously  in  separate  cameras.  One  negative  is  de- 
veloped and  projected  on  a  screen  on  which  the  background  is  then 
drawn,  a  non-actinic  area  being  left  where  the  foreground  appears. 
The  frames  of  the  other  film,  exposed  to  the  action,  are  then  re- 
exposed  one  by  one  to  the  drawing,  so  as  to  add  the  desired  back- 
ground, the  necessary  changes  in  the  non-actinic  area  of  the 
drawing  being  made  between  frames  according  to  the  changes  in 
position  of  the  action. 

What  seems  to  be  a  worth-while  detail  in  the  process  of  making  the 
traveling  mask  is  shown  in  patent  No.  1,840,669,  issued  January  12, 
1932,  to  M.  Handschiegl.  This  patent  describes  the  use  of  two  super- 


posed  films  in  the  camera,  both  films  being  exposed  to  the  action. 
One,  preferably  the  rear  one,  is  developed  for  contrast,  and  is  then 
positioned  in  front  of  the  other,  still  undeveloped,  so  as  to  protect 
the  exposure  of  the  action  during  the  exposure  of  the  background. 

A  companion  patent,  No.  1,840,670,  issued  to  the  same  inventor 
and  on  the  same  date,  gives  a  terse  summary  of  the  traveling  mask 
processes,  and  seeks  to  claim  a  process  in  which  a  positive  print  of  the 
desired  background  is  used  with  the  mask,  necessitating  only  one 
mask.  The  claims,  however,  seem  narrow,  and  of  doubtful  validity. 

The  mask  and  screen  processes  described  above  are  designed  with 
the  idea  of  photographing  the  foreground  and  the  background  sepa- 
rately, and  of  obscuring  complementary  areas  of  the  film  during  one 
or  both  exposures  by  means  of  an  opaque  mask,  or  shield,  this  being 
the  essential  element,  whereby  the  composited  element  is  fitted  into 
the  opening  of  the  other  exposure  made  by  the  shield. 


It  has,  of  course,  long  been  known  that  stage  settings  could  ad- 
vantageously be  reproduced  from  full-size  drawings,  and  it  seems  to 
have  been  early  appreciated  that  a  stage  background  could  be  pro- 
duced by  optically  projecting  a  small  transparency,  such  as  a  lantern 
slide,  on  a  translucent  screen  serving  as  a  back  drop,  as  is  shown  in 
patent  No.  486,606,  issued  to  F.  Seymour  on  November  22,  1892. 
This  patent  shows  a  stage  setting  consisting  of  a  translucent  screen 
upon  which  the  scene  is  projected  by  a  stereopticon,  the  actor  being 
positioned  in  front  of  the  screen.  Photographing  of  the  stage  and 
action  is  not,  however,  suggested  in  this  patent. 

The  first  suggestion  of  composite  photography,  for  a  still  picture, 
by  directly  photographing  a  normal  figure  or  foreground  against  a 
projected  background,  is  found  in  patent  No.  656,769,  issued  August 
28,  1900,  to  R.  M.  Hunter.  However,  this  patent  involves  photo- 
graphing separately  the  foreground  or  figure,  and  the  background, 
probably  because  of  differences  in  illumination,  and  the  difference  in 
exposure  time  for  the  two.  It  was,  of  course,  possible  to  do  this  in 
still  photography,  where  the  subject  could  stand  still  long  enough  to 
become  the  necessary  silhouette  before  the  projected  background. 

The  process  of  simultaneously  exposing  the  foreground  and  the 
background  by  projection,  in  still  photography,  is  disclosed  in  patent 
No.  1,053,887,  issued  February  18,  1913,  to  H.  Sontag.  This  patent 
also  describes  the  use  of  a  non-actinic  front  surface  on  the  translucent 

292  H.  D.  HINELINE  [J.  S.  M.  P.  E. 

screen,  for  reducing  the  effect  of  front  light  in  degrading  the  contrast 
of  the  projected  background. 

A  variant,  in  which  the  projection  screen  covers  part  of  the  subject, 
is  shown  in  patent  No.  1,133,311,  issued  March  30,  1915,  to  W.  W. 
Newcomb,  also  for  still  photography.  This  patent  shows  front 
projection,  and  photographic  exposure  from  the  front.  (The  pro- 
jected matter  is  described  as  pictures  of  women's  clothing.  The 
subject  would  stand  behind  the  screen,  her  head  showing  above  it, 
and  be  photographed  to  show  how  she  would  appear  in  her  new 

What  may  be  considered  to  be  an  off-shoot  from  the  direct  line  of 
development  of  projection  processes  is  found  in  patent  No.  1,263,355. 
issued  April  16,  1918,  to  P.  Artigue.  This  patent  describes  a  process 
for  making  animated  shadowgraphs,  in  which  the  background  scene 
is  sketched  on  a  translucent  screen  illuminated  from  the  rear  by  a 
point  source  of  light,  the  desired  shadows  being  thrown  upon  it  by 
the  actors,  to  be  photographed  together  with  the  background. 

The  first  suggestion  of  simultaneous  projection  and  photographing 
for  motion  picture  work  is  found  in  patent  No.  1,270,778,  issued 
July  2,  1918,  to  A.  D.  Brixey.  This  patent  discloses  means  for  add- 
ing dialog  inscriptions  to  a  motion  picture  film  (before  the  advent  of 
sound)  by  projecting  the  successive  frames  upon  a  translucent  screen 
before  the  camera,  and  holding  up  to  the  screen  a  card  inscribed  with 
appropriate  lettering  and  provided  with  a  "leader"  that  would  follow 
the  mouth  of  the  character  supposed  to  be  speaking.  The  screen 
and  card  are  then  photographed  to  produce  the  desired  film. 

Still  another  off-shoot  process  is  disclosed  in  patent  No.  1,278,117, 
issued  September  10,  1918,  to  J.  S.  Dawley,  describing  a  process  in 
which  the  background  is  inserted  into  the  picture  by  reflection  from 
a  plate  of  glass  in  the  line  of  sight  of  the  lens,  the  actors  being  in 
the  direct  line.  The  way  in  which  ghosting  is  avoided  is  not  given, 
and  this  lack  may  be  fatal  to  the  process.  It  is  doubtful  whether 
this  should  really  be  considered  as  a  projection  process. 

Another  forward  step  is  shown  in  patent  No.  1,301,538,  issued  to 
L.  S.  Brainerd,  on  April  22,  1919.  A  coupled  projector  and  camera 
operate  in  synchronism.  The  camera  and  the  projector  are  placed 
side  by  side  before  a  stage,  which  has  an  opaque  screen  at  the  rear. 
The  background  is  projected  upon  the  screen  and  actors  together, 
no  provision  being  made  to  prevent  the  projected  image  from  being 
superposed  on  the  actors.  It  may  be  noted  that  all  the  claims  in 


this  patent  are  drawn  with  the  phrase  "cartoon  pictures"  for  the 
projected  material. 

Attention  may  well  be  called  again  to  the  first  of  the  Brainerd 
patents,  No.  1,296,471,  previously  mentioned,  as  the  claims  in  it  may 
well  be  more  pertinent  to  a  projection  process  than  to  a  mask  process. 

The  third  Brainerd  patent,  No.  1,307,846,  issued  June  24,  1919, 
carries  the  idea  still  farther  by  claiming  the  process,  although  the 
disclosure  is  much  the  same  as  that  of  the  second  Brainerd  patent, 
No.  1,301,538. 

It  may  be  noted  that  at  this  stage,  work  on  projection  processes 
seems  to  have  languished  for  a  considerable  time,  nearly  ten  years, 
the  Brainerd  patents  having  been  applied  for  in  1915,  and  the  next 
issued  patent  appearing  in  1925.  This  patent,  No.  1,601,886,  was 
issued  on  October  5,  1926,  to  E.  Schufiftan,  and  discloses  a  camera, 
a  partly  silvered  mirror  in  front  of  the  camera  lens,  a  screen  on  which 
the  background  is  projected  adjacent  to  one  face  of  the  mirror,  and 
the  stage  setting  and  actors  before  the  other  side  of  the  mirror,  the 
two  being  composited  by  reflection  and  direct  vision  through  adja- 
cent reflecting  and  transmitting  areas  of  the  mirror.  A  synchroniz- 
ing drive  connection  between  the  camera  and  the  projector  is  well 
shown.  All  the  claims  seem  to  be  limited  by  the  inclusion  of  the 
partly  silvered  mirror. 

A  very  nearly  similar  system  is  disclosed  in  another  Schufftan 
patent,  No.  1,690,039,  issued  October  30,  1928.  These  patents 
must  be  examined  in  the  original,  to  see  the  minutiae  of  detail,  and 
the  differences  in  the  respective  disclosures,  and  claims. 

The  projection  idea  is  applied  to  the  manufacture  of  animated 
cartoons  in  patent  No.  1,760,156,  issued  May  27,  1930,  to  N.  H. 
Mann.  The  principal  function  of  the  projection,  however,  is  to 
produce  photoprints  from  the  motion  negative,  from  which  photo- 
prints cut-outs  are  applied  to  the  successive  cartoon  card  sketches. 

The  last  patent  to  be  mentioned  in  the  field  of  projection  composit- 
ing is  No.  1,827,924,  issued  October  20,  1931,  to  F.  D.  Williams, 
showing  a  number  of  details  of  value  in  projection  processes,  including 
the  displacement  of  the  projector  sidewise  from  the  normal  line  of 
the  screen  so  as  to  avoid  the  "hot  spot,"  the  use  of  two  projectors 
throwing  different  picture  components  upon  the  screen,  the  use  of 
superposed  films  in  the  projector,  double  exposure  of  the  camera  film 
to  successively  projected  images  from  the  projector,  etc. 

The  projection  method  of  compositing  is  thus  shown  to  have  been 

294  H.  D.  HINELINE  [j.  S.  M.  P.  E. 

brought  to  a  high  stage  of  development,  becoming  convenient  and 
flexible  in  application,  and  possessing  substantially  fewer  difficulties 
than  are  inherent  in  the  mask  processes.  The  most  serious  objection 
to  the  process  is  said  to  be  the  loss  of  detail  and  definition  in  the  back- 
ground copied  from  the  screen. 


Another  interesting  process  involves  the  differentiation  between 
the  foreground  and  the  background  by  means  of  color  combinations, 
the  process,  broadly  stated,  being  that  of  using  a  positive  trans- 
parency of  one  picture  component,  which  is  transparent  to  the  fore- 
ground image  but  is  printed  on  the  film  for  the  background  image. 
This  process  has  been  largely  developed  by  Dunning  and  Portiere)', 
but  a  small  amount  of  prior  art  is  worth  noticing. 

The  first  item  of  this  prior  art  is  patent  No.  858,162,  issued  June 
25,  1907,  to  F.  J.  Dischner,  which  discloses  a  process  in  which  a 
positive  of  the  desired  background  is  positioned  in  front  of  the  nega- 
tive material  in  the  camera,  and  an  illuminated  back-screen  used 
behind  the  subject.  The  light  from  the  back-screen  prints  the  back- 
ground positive  on  the  negative  material,  as  a  negative;  while  the 
foreground  subject  makes  a  silhouette  against  the  back-screen,  and 
prevents  exposure  over  the  foreground  area.  The  positive  and  the 
lighted  screen  are  then  removed,  and  the  foreground  subject  is  lighted 
and  photographed  without  change  of  position.  Another  patent, 
No.  967,025,  issued  August  9,  1910,  to  Leonard  and  Oldaker,  shows  a 
camera  structure  adapted  to  this  process.  Both  are  for  still  rather 
than  motion  picture  photography. 

The  first  appearance  of  the  idea  of  employing  color  for  the  separa- 
tion occurs  in  patent  No.  1,613,163,  issued  January  4,  1927,  to  C.  D. 
Dunning.  This  patent  suggests  that  the  original  negative  of  the 
background  be  printed  to  a  positive,  which  is  then  color  toned  and 
tinted,  placed  into  the  camera  with  panchromatic  film  stock,  and  the 
foreground  subject  photographed  through  it  against  a  colored  back- 
ground. As  far  as  can  be  judged,  the  idea  is  to  make  the  positive 
uniformly  transmissive  to  white  light,  but  non-uniformly  trans- 
missive  to  colored  light,  thereby  making  possible  the  exposure  by 
white  light  passing  through  it  from  the  foreground  subject,  and  the 
printing  of  the  positive  simultaneously  by  colored  light  en  silhouette 
around  it. 

A  much  clearer  disclosure  is  found  in  patent  No.  1,673,019,  issued 


June  12,  1928,  to  R.  J.  Pomeroy.  This  patent  describes  the  use  in 
the  camera  structure  of  a  dye  positive  of  the  desired  background, 
with  panchromatic  negative  stock;  and  a  back  curtain,  placed 
before  the  camera  and  behind  the  action,  of  a  color  contrasting  with 
the  dye  positive,  the  action  being  illuminated  with  light  of  the  same 
color  as  the  dye  positive.  The  foreground  light  then  passes  through 
the  positive  unhindered,  making  the  exposure ;  while  the  background 
light,  en  silhouette,  prints  the  positive,  making  the  background  ex- 
posure. This  patent  appears  to  contain  the  broadest  claims  to  the 

The  next  patent  in  order  is  No.  1,686,987,  issued  October  9,  1928, 
also  to  R.  J.  Pomeroy,  which  shows  a  process  for  combining  separately 
photographed  action  and  background  in  a  printer  by  the  aid  of  colored 
lights.  The  action  is  photographed  before  a  white  screen,  so  as.  to  be 
surrounded  by  an  opaque  mat.  From  this  negative  is  made  a  dye 
positive,  in  which  the  action  printed  in,  say,  blue,  is  surrounded  by  a 
red  field.  This  is  combined  with  a  light  print  of  the  background  also 
dyed  blue.  The  two  are  superposed  on  panchromatic  stock  in  the 
printer,  and  printed  by  mixed  red  and  blue  light,  thus  producing  the 
desired  composite  negative.  The  light  blue  background  print  has  a 
negligible  effect  under  the  heavy  blue  foreground  action,  which  is 
printed  by  the  blue  light,  but  the  light  blue  print  strongly  contrasts 
with  the  red  light  through  the  silhouette  around  the  action.  This 
is  as  ingenious  and  interesting  a  process  as  is  found  in  the  art,  because 
of  the  nice  balance  of  elements;  although  it  is  far  from  the  simplest 
to  work,  nor  does  it  promise  better  results  than  other  processes. 

Still  another  variant  is  shown  in  patent  No.  1,715,510,  also  issued 
to  R.  J.  Pomeroy,  on  June  4,  1929.  In  this  form,  the  action  is  photo- 
graphed before  a  non-actinic  background,  the  negative  being  toned 
blue,  on  a. clear  field.  A  blue-dye  background-negative-transparency 
is  positioned  in  the  camera  in  front  of  a  panchromatic  film,  the  camera 
being  trained  on  the  action  negative,  which  is  illuminated  with  red 
light.  The  negative  is  front-lighted  in  blue,  and  the  respective 
lights  print  the  two  negatives  on  the  panchromatic  film  in  the 

A  nice  outline  of  the  color  differentiation  compositing  process 
with  improvements  is  found  in  patent  No.  1,776,269,  issued  Septem- 
ber 23,  1930,  to  R.  J.  Pomeroy,  the  improvement  specifically  disclosed 
being  that  of  using  a  negative  film  of  the  background  positive  print, 
dyed  in  a  color  such  as  yellow,  with  the  blue  background  positive 

296  H.  D.  HINELINE  [j.  S.  M.  P.  E. 

print,  so  as  to  counterbalance  absorption,  by  the  print,  of  light  of 
the  same  color  as  the  print. 

The  latest  of  the  patents  dealing  with  this  process  is  No.  1,788,740, 
issued  January  13,  1931,  also  to  R.  J.  Pomeroy,  disclosing  an  interest- 
ing procedure  of  using  the  color-separation  method  with  a  silver 
print  for  the  background  scene.  The  process  employs  a  split  light 
beam  with  color  filters,  complementary  lights  on  action  and  back 
screen,  and  panchromatic  film,  the  foreground  and  background  ex- 
posures being  made  on  opposite  sides  of  the  film.  One  light  beam 
emanates  from  the  action;  the  other  is  en  silhouette  around  the 
action,  and  prints  the  silver  positive  on  the  reverse  side  of  the  film. 
This,  of  course,  involves  the  problem  of  registration  of  the  two  beams 
on  the  opposite  sides  of  the  negative  film. 


Another  procedure,  which  has  attained  to  a  separate  status  in  the 
field,  is  identified  by  the  phrase  "glass  shot."  In  this  process,  in 
its  customary  form,  the  desired  background  is  painted,  in  miniature, 
on  a  plate  of  glass  which  is  placed  near,  and  in  front  of,  the  camera. 
Part  of  the  glass  is  left  clear  so  that  the  action  may  be  photographed 
through  it.  This  process  is  strictly  a  variant  of  the  stationary  mask 
process,  but  having  attained  to  a  separate  field,  may  be  separately 

The  first  mention  of  a  process  suggesting  this  method  occurs  in 
patent  No.  45,449,  issued  December  13,  1864,  to  Wm.  Callcott. 
This  patent  discloses  simply  a  stage  illusion,  in  which  successive  glass 
plates,  on  which  the  desired  scenery  is  painted  with  light-translucent 
paint,  are  successively  illuminated,  the  rear  ones  being  visible  through 
the  front  ones.  No  photography  seems  to  have  been  involved  in 
the  process.  » 

The  next  suggestion  of  interest  is  found  in  patent  No.  1,019,141, 
issued  March  5,  1912,  to  A.  Engelsmann.  A  glass  plate  serves  to 
reflect  light  from  depressed  screens  carrying  moving  pictures  of  the 
actors  only,  without  the  background.  The  glass  is  placed  in  front 
of  a  painted  drop;  a  pseudo-stereoscopic  appearance  is  effected, 
the  motion  picture  actors  being  expected  to  give  the  impression  of 
being  in  front  of  the  drop. 

An  interesting  use  of  a  glass  plate — not  quite  a  "glass  shot"  as 
now  understood — is  shown  in  patent  No.  1,235,871,  issued  August  7, 
1917,  to  C.  M.  Aument.  This  patent  discloses  a  cartoon  process, 


in  which  the  permanent  background  is  drawn  on  the  glass,  the  mov- 
ing figures  being  sketched  on  it  in  successive  positions  and  guide 
sketches  being  used  on  the  back  of  the  glass  to  aid  in  making  the  main 
sketches,  which  are  then  photographed.  Still  another  cartoon  process 
employing  a  glass  plate  is  disclosed  in  patent  No.  1,263,355,  issued 
April  16,  1918,  to  P.  Artigue,  previously  mentioned.  The  desired 
background  is  sketched  on  a  translucent  screen,  and  the  actors  are 
silhouetted  on  the  screen  by  a  single  rear  light.  This  is  not  quite  a 
"glass  shot,"  although  it  has  most  of  the  elements  of  a  glass  shot. 

Still  another  approach  to  the  glass  shot  idea  is  found  in  patent  No. 
1,278,117,  issued  September  10,  1918,  to  J.  S.  Dawley.  In  this 
process,  a  glass  screen  in  front  of  and  near  the  camera  has  projected 
upon  it  the  desired  background  scene,  while  the  actors  are  on  a  screen 
stage  of  normal  size,  beyond  the  glass. 

Another  interesting  suggestion  is  found  in  patent  No.  1,296,471, 
issued  March  4,  1919,  to  L.  S.  Brainerd,  and  previously  mentioned. 
It  is  of  interest  in  that  it  shows  means  for  photographing  both  the 
actors  and  a  miniature  sketch  with  the  same  camera,  on  the  same 

The  next  pertinent  patent  to  be  issued  was  No.  1,372,811,  to  W.  L. 
Hall,  on  March  29,  1921.  This  patent  shows  in  elaborate  detail  the 
steps  to  be  taken  in  matching  the  miniature  on  the  glass,  in  tone  and 
perspective,  to  the  desired  foreground  by  means  of  targets,  charts, 
and  tone  scales,  and  gives  a  good  outline  of  the  whole  procedure. 
The  claims  refer  to  the  broad  process,  and  to  the  details. 

It  may  be  noted  that  glass  shots  are  made  with  the  miniature  of 
the  background  on  a  glass  plate  as  a  matter  of  convenience;  however, 
it  does  not  appear  that  this  is  the  only  possible  way,  since  similar 
results  may  be  attained  with  the  miniature  on  an  opaque  sheet  in 
which  openings  are  cut  for  the  line  of  sight  to  the  action  in  full  scale, 
or  in  the  solid,  with  similar  openings. 

This  method  of  working  is  disclosed  in  patent  No.  1,476,885, 
issued  December  11,  1923,  to  D.  W.  Griffith.  Here  is  used  a  screen 
having  a  hole  cut  in  it.  The  screen  is  appropriately  painted,  and  an 
actor  may  work  in  front  of  it,  while  another  screen  and  actors  may  be 
visible  through  the  opening. 

The  "glass  shot"  idea  is  carried  still  farther  in  patent  No.  1,540,213, 
issued  June  2,  1925,  to  O.  R.  Hammeras.  The  system  disclosed  is 
stated  to  be  an  improvement  over  the  Hall  patent  No.  1,372,811, 
which  improvement  seems  to  lie  in  the  idea  of  building  sets  to  a  point 

298  H.  D.  HlNELINE  [J.  S.  M.  P.  E. 

just  above  the  heads  of  the  actors,  and  completing  the  top  of  the  set 
by  a  painted  miniature  on  a  glass  plate.  The  claims  seem  to  be  drawn 
to  the  idea  of  marking  the  outlines  of  the  fixed  scenery  on  the  glass 
plate  and  completing  the  miniature  from  such  guide  lines,  thereafter 
photographing  from  and  through  the  glass. 

The  equivalent  of  a  glass  shot,  that  is,  a  miniature  drawn  or  con- 
structed of  opaque  material,  without  the  glass,  is  described  in  patent 
No.  1,574,464,  issued  February  23,  1926,  to  J.  Bartholowsky.  This 
patent  shows  a  bottom  portion  of  a  set  constructed  full-scale  for  the 
actors;  and  a  top  portion,  in  miniature  and  much  nearer  the  camera, 
with  the  joining  margins  aligned  before  the  camera,  the  perspective 
of  the  miniature  part  of  the  set  being  adapted  to  its  distance  from  the 

The  details  of  "glass  shots"  are  still  further  developed  in  patent 
No.  1,742,680,  issued  January  7,  1930,  to  P.  Artigue.  The  main 
feature  of  the  disclosure  is  the  use  of  filter  colors,  or  dyes,  on  the  glass 
to  modify  the  appearance  of  the  scene  behind  the  glass. 

The  last  patent  to  be  noticed  on  the  subject  of  glass  shots  is  No. 
1,764,490,  issued  June  17,  1930,  also  to  P.  Artigue,  the  main  point 
of  interest  relating  to  the  mounting  of  the  glass  and  miniature  on  a 
staging  with  the  camera  so  as  to  permit  the  two  to  be  moved  about 
as  for  panoramic  views,  without  disturbing  the  relation  of  the  glass 
to  the  camera.  In  view  of  the  many  devices  for  movable  cameras 
with  all  sorts  of  attachments,  a  question  may  be  raised  whether  such 
a  system  as  here  disclosed  involves  invention. 


One  worker  in  the  field,  Eugene  Schiifftan,  has  concentrated  on  a 
variant  of  the  ''glass  shot,"  in  which  is  employed  a  glass  plate,  partly 
reflecting,  partly  transmitting,  that  seems  to  have  been  developed  to 
a  substantial  degree  of  completion.  In  each  instance  he  uses  a  glass 
plate  that  is  partly  silvered,  but  has  unsilvered  transparent  portions. 
This  glass  is  placed  before  the  camera  lens,  the  camera  beam  being 
divided  so  as  to  bring  light  upon  the  film  from  two  subjects. 

The  first  of  his  patents,  No.  1,569,789,  issued  January  12,  1926, 
discloses  a  mirror  partly  silvered  over  an  area  of  the  camera  field  of 
view  in  which  the  action  is  to  occur,  and  unsilvered  over  an  area  of 
the  field  of  view  in  which  a  miniature  set  is  to  appear.  The  action 
is  then  viewed  by  reflection,  and  the  miniature  set  is  viewed  by  trans- 
mission through  the  glass.  The  reverse  procedure  is,  of  course, 


possible.  Various  details  are  outlined,  such  as  an  adjustable  seg- 
mental  mirror,  etc. 

His  second  patent,  No.  1,601,886,  issued  October  5,  1926,  deals 
mainly  with  the  mechanical  equipment  for  the  process.  It  includes 
such  items  as  a  small  projected  background,  a  supplemental  collecting 
lens  to  correct  the  focus  on  the  miniature,  mechanical  details  of  the 
camera  and  miniature,  etc. 

Two  other  patents,  Nos.  1,606,482-3,  issued  on  November  9,  1926, 
furnish  still  other  details  of  the  process  and  apparatus,  including  the 
method  of  operating  it,  of  preparing  the  mirror  and  the  miniature 
drawing,  registration,  blending,  etc. 

Another  patent,  No.  1,613,201,  issued  January  4,  1927,  discloses 
a  special  double-lens  camera,  which  is  combined  with  a  considerable 
number  of  partly  silvered  mirrors  for  assembling  a  plurality  of  sepa- 
rate picture  elements.  This  idea  is  extended  in  a  somewhat  better 
mechanical  form  in  patent  No.  1,627,295,  issued  May  3,  1927. 

Still  another  of  this  group  of  patents,  No.  1,636,112,  issued  July 
19,  1927,  shows  and  claims  the  details  of  a  large  collecting  lens  in 
combination  with  the  mirror,  for  modifying  the  effective  focus  of  the 
camera  lens  on  the  reflected  image,  bringing  both  reflected  and  trans- 
mitted light  beams  to  an  equally  sharp  focus. 

The  last  of  this  group  of  patents  to  be  considered  is  No.  1,690,039, 
issued  October  30,  1928.  This  is  a  division  of  an  earlier  application, 
issued  as  patent  No.  1,569,789,  and  discloses  and  claims  the  pro- 
jection of  a  miniature  upon  a  translucent  screen,  in  combination  with 
the  partly  silvered  mirror,  camera,  and  full-scale  scenery  and  actors. 


In  any  composite  process  the  most  troublesome  problem  is  that  of 
accurately  registering  the  respective  composited  parts,  the  problem 
being  most  acute  in  traveling  mask  processes,  and  least  acute  in  the 
color-separation  processes.  Because  of  the  convenience  of  mask 
processes,  attempts  have  been  made  to  develop  what  may  be  called  a 
"self -masking"  process. 

The  first  of  these,  as  previously  mentioned,  is  shown  in  patent  No. 
1,503,731,  issued  to  J.  B.  Walker,  on  August  5,  1924.  Walker  pro- 
poses to  swell  the  gelatin  film  so  as  to  obtain  a  relief  image  of  the  fore- 
ground or  action  exposure,  after  development,  but  before  fixing.  A 
coat  of  ink  or  dye  is  then  applied  to  the  raised  portions  (the  action 
may  be  photographed  before  a  non-actinic  screen  for  background). 

300  H.  D.  HlNELINE 

The  film  is  then  dried,  reexposed  on  the  other  component,  redeveloped, 
etc.,  and  the  ink  removed.  Obviously,  success  depends  upon  inking 
only  the  foreground,  and  all  of  it. 

The  next  similar  suggestion  is  found  in  Patent  No.  1,697,315, 
issued  January  1,  1929,  to  M.  Handschiegl.  This  patent  proposes  a 
process  of  photographing  action  on  film  that  is  not  color-sensitive, 
developing,  and  printing  the  unfixed  film  on  panchromatic  stock  by 
red  light.  A  second  print,  made  from  this  print,  forms  a  mask  to 
protect  the  first  exposure  while  a  second  is  added,  after  which  a 
second  development,  etc.,  yields  the  composite  negative.  This  is  not 
quite  a  self -masking  process,  but  is  of  interest  for  the  double  develop- 

M.  Osann  suggests,  in  Patent  No.  1,698,448,  January  8,  1929, 
toning  a  developed  but  unfixed  film  of  the  foreground,  photographed 
before  a  non-actinic  screen,  to  increase  the  opacity  of  the  image.  He 
uses  a  cupric  ferrocyanide  toner  for  the  more  light  absorbent  red 
image.  A  second  exposure  is  made  over  the  toned  image,  developed, 
etc.,  for  the  background.  Panchromatic  print  film  with  the  negative 
is  suggested,  probably  to  avoid  the  density  unbalance  between  the 
two  images.  A  simpler  way  might  be  to  tone  the  second  image. 

R.  J.  Pomeroy,  in  Patent  No.  1,755,129,  April  15,  1930,  suggests  a 
similar  process,  toning  the  first  image  with  a  quinone  toner,  reexposing 
etc.,  the  toning  being  removed  by  the  fixing  bath.  He  also  suggests 
a  selective  desensitization  as  by  phenosafranine,  to  protect  the  first 
image  area.  He  also  suggests,  in  Patent  No.  1,755,130,  same  date, 
a  pigmented  casein  coating,  applied  to  the  film  after  foreground 
development.  Bleaching  then  hardens  both  the  film  and  casein 
coating  over  the  image,  the  rest  being  removed,  producing  a  self -mask, 
over  which  the  second  exposure  is  made,  developed,  etc.,  and  the 
casein  coating  removed  by  mild  caustic. 

This  assortment  of  processes  should  provide  one,  at  least,  which  is 
usable  under  any  given  circumstances,  although  each  has  its  limita- 
tions. It  should  also  be  noted  that  most  of  the  above-mentioned 
patents  are  still  in  force.  For  further  information  on  the  processes 
described,  copies  of  the  patents  may  be  obtained  from  the  Com- 
missioner of  Patents,  Washington,  D.  C. 



Summary. — The  physical  and  photographic  properties  of  the  lenticular  screen 
process  of  producing  motion  pictures  in  color,  as  developed  by  Berthon,  and  later 
known  under  the  name  Keller-Dorian  and  commercialized  in  the  16-mm.  field  under 
the  name  Kodacolor,  are  briefly  described.  The  author  traces  the  development  of 
the  process  from  the  earlier  mosaic  screen  process,  and  after  giving  consideration  to 
the  technical  problems  involved,  indicates  that  the  situation  obtaining  at  present 
may  be  regarded  as  one  stage  of  a  development  leading  up  to  the  application  of  the 
lenticular  screen  process  to  the  35-mm.  field  as  well  as  the  16-mm.  field. 

Processes  of  making  motion  pictures  in  natural  colors  must  satisfy 
at  least  the  following  principal  requirements  in  order  to  be  technically 
and  practically  successful: 

(1)  The  photographic  manipulation  and  apparatus  must  be  simple. 

(2)  The  process  must  provide  sufficient  color  saturation  and  resolution; 
that  is,  the  color  elements  must  be  small  enough  to  be  unobjectionable. 

(3)  It  must  be  possible  to  make  prints  from  an  original  exposure. 

(4)  The  process  must  make  efficient  use  of  the  available  light,  both  in  making 
camera  exposures  and  in  projecting  the  pictures  on  the  screen. 

It  would  be  impossible,  within  a  limited  space,  to  mention  all 
the  processes  that  have  been  suggested  and  tested,  or  are  still  in  the 
experimental  stage,  for  producing  colored  motion  pictures.  A  re- 
view of  present  methods  is  given  by  J.  Eggert.1 

This  paper  describes  briefly  the  physical  and  photographic  princi- 
ples of  the  lenticular  screen  process  as  developed  by  the  French 
optician,  A.  Berthon,  in  1908.  In  1913,  Berthon  and  Keller-Dorian 
formed  the  "Societe  anonyme  du  film  en  couleur  Keller-Dorian;" 
and,  under  the  name  of  Keller-Dorian,  this  process  is  widely  known. 
Out  of  this  company,  the  "Societe  Cinechromatique"  was  formed  in 
France,  while  Kodak  took  over  the  patents  and  commercially 
applied  the  lenticular  screen  process  to  16-mm.  film  under  the  name 

*  Translated  from  Filmtechnik,  8  (Sept.  3,  1932),  p.  1. 


302  F.  WEIL  [j.  S.  M.  P.  E. 

of  Kodacolor.  Recently,  Agfa  has  also  produced  a  16-mm.  film  based 
on  the  same  principles,  called  Agfacolor. 

Up  to  the  present  time,  both  companies  have  restricted  themselves 
to  the  production  of  16-mm.  film  only.  The  amateur  usually  takes 
his  pictures  outdoors,  where  he  finds  a  large  variety  of  colors  and  a 
wide  range  of  light  intensity;  the  lenses  of  amateur  movie  cameras 
have  sufficient  focal  depth  even  at  large  apertures.  Moreover,  the 
lenticular  screen  process  is  so  simple  that  only  small  and  easily 
adaptable  accessories  are  required  in  order  to  apply  it  to  any  existing 
camera.  As  to  the  photography,  there  is  no  difference  between  this 
process  and  the  reversal  process  generally  used  in  16-mm.  film  technic. 
Therefore,  the  technical  development  of  this  field  has  not  been  re- 
tarded by  unsolved  problems  of  a  satisfactory  printing  process. 
The  16-mm.  picture  is  projected  only  to  a  limited  size  and  brilliancy 
on  the  screen. 

The  fact,  however,  that  this  process  is  being  applied  only  to  16-mm. 
film  should  not  lead  to  the  conclusion  that  it  can  not  be  applied  to 
the  35-mm.  standard  motion  picture  film.  The  situation  at  present 
may  be  regarded  as  one  stage  of  a  development  leading  to  the 
application  of  the  lenticular  screen  process  to  the  35-mm.  field  as 

In  certain  respects,  the  lenticular  screen  process  in  its  photo- 
graphic and  optical  principles  is  an  extension  of  the  mosaic  screen 
process,  long  ago  introduced  into  amateur  photography.  Indeed 
it  might  be  regarded  as  a  color  screen  process  modified  for  motion 
picture  purposes.  Both  the  lenticular  and  mosaic  screen  processes 
are  so-called  additive  processes ;  that  is  to  say,  the  required  colors  are 
produced  by  blending  three  primary  colors.  A  combination  of  red  and 
green  produces  yellow;  red  and  blue  produce  purple;  blue  and  green 
produce  bluish  green.  Red,  blue,  and  green  when  properly  com- 
bined, produce  white.  Conversely,  it  is  possible  to  analyze  any  given 
color,  with  respect  to  the  proportion  of  red,  green  or  blue  contained 
in  it,  simply  by  using  filters  of  these  colors.  The  color  may  then  be 
reproduced  by  mixing  light  of  these  colors  in  the  same  proportions. 
This  separation,  or  analysis,  of  the  color  can  be  accomplished  photo- 
graphically by  exposing  the  film  to  the  object  through  the  color 
filters,  either  simultaneously  or  in  succession,  using  one  or  several 
lenses.  For  reproduction,  these  exposures  must  be  optically  super- 
imposed in  perfect  registration.  With  a  color  screen  or  lenticular 
screen,  however,  the  tri-color  analysis  can  be  made  in  a  single  ex- 


posure,  by  dividing  the  photographic  coating,  in  one  way  or  another, 
into  numerous  small  units,  each  unit  being  fitted  with  a  red,  green, 
and  blue  filter.  The  smaller  the  units,  the  higher  the  resolving 
power.  Theoretically,  these  units  should  not  be  so  large  as  to  come 
within  the  resolving  power  of  the  eye  (visual  angle  of  1  minute, 
corresponding  to  about  0.02  mm.  at  the  natural  viewing  distance). 
Each  area  is  fitted  with  a  composite  tri-colored  window  through 
which  the  light  from  each  individual  area  of  the  object  passes  to  the 
emulsion  coating. 

In  the  mosaic  screen  process  we  find  the  simplest  application  of 
this  principle.  Between  the  emulsion  coating  and  the  film  (or  glass), 
we  find  the  color  screen,  an  even  blending  of  red,  green,  and  blue 
transparent  grains  of  starch  or  bakelite,  irregularly  dispersed.  The 
mixture  of  the  grains  is  never  quite  uniform,  as  the  formation  of 
small  clumps  of  grains  can  not  be  avoided.  The  exposure  of  the 
emulsion  is  always  made  through  the  screen.  Each  group  of  differ- 
ently colored  grains  forms  a  screen  unit,  in  the  sense  already  ex- 
plained, and  the  light  rays,  passing  through  the  grains,  produce  a 
photographic  effect  according  to  the  primary-color  content  of  the 
rays.  In  order  to  see  the  original  in  its  true  colors,  it  is  necessary 
to  subject  the  developed  film  to  a  reversal  process,  because  the  usual 
negative  development  produces  only  the  complementary  colors. 

Unfortunately,  the  mosaic  process  can  not  be  used  for  motion 
pictures.  First  of  all,  the  enlargement  necessary  for  motion  pictures 
would  magnify  the  grains  of  the  color  screen  to  a  size  within  the 
resolving  power  of  the  eye,  thus  making  the  individual  grains  visible. 
Furthermore,  on  account  of  the  random  distribution  of  the  color 
grains,  local  aggregations  of  similarly  colored  grains  can  not  be 
avoided.  A  greater  difficulty,  however,  is  the  fact  that  the  random 
distribution  of  the  screen  elements  over  the  entire  image  surface — 
their  positions  relative  to  the  perforations  of  the  film — changes  with 
each  and  every  frame  of  the  film.  On  account  of  the  intermittency  of 
projection,  these  two  effects  cause  a  violent  irregular  movement  of 
the  colored  grains,  producing  a  disturbing  visible  effect  particularly 
on  larger  areas  of  uniform  color. 

In  order  to  adapt  the  color  screen  process  to  motion  pictures, 
it  would  be  necessary  to  arrange  the  color  elements  in  a  regular 
pattern  parallel  to  the  edges  of  the  film.  Thus  the  elements  would  no 
longer  be  distributed  haphazardly.  Naturally,  the  manufacture  of 
such  an  extremely  fine  screen  involves  many  practical  difficulties; 

304  F.  WEIL  [j.  s.  M.  P.  E. 

nevertheless,  commercial  experimentation  has  already  been  successful 
and  is  being  continued.2 

The  lenticular  screen  process  as  developed  by  Berthon  solved  the 
problem  by  very  simple  and  ingenious  means.  Berthon  abandoned 
from  the  very  beginning  the  idea  of  attaching  the  niters,  correspond- 
ing to  the  different  surface  elements,  to  the  film,  and  of  providing  the 
film  itself  with  a  real  color  screen.  On  the  contrary,  the  screen  is 
produced  on  the  film  optically  during  the  exposure,  and  on  the  screen 
during  projection.  The  film  serves  only  as  a  support  for  an  optical 
system  of  tiny  cylindrical  lenses  embossed  on  the  film  base.  The 
width  of  each  lens  is  about  0.028  to  0.043  mm.,  the  focal  length  being 
0.1  to  0.14  mm.  The  lenticular  screen  is  adjusted  to  the  taking  or 
projecting  lens  system,  as  shown  in  Fig.  1.  A  color  filter  having 
three  colored  areas — red,  green,  and  blue — in  three  parallel  sections, 
is  placed  either  inside  or  outside  the  lens  system.  It  does  not  matter 
where  the  filter  is  placed,  so  long  as  it  controls  the  aperture.  Further- 
more, the  filter  diaphragm,  or  its  virtual  image,  must  not  obscure 
the  entrance  pupil  of  the  lens  from  any  part  of  the  film.  The  outer 
parts  of  the  filter  would  be  so  obscured,  viewed  from  the  margins 
of  the  film  area.  This  defect  will  be  more  fully  described  later. 
Once  the  position  of  the  filter  has  been  fixed  for  exposing  the  film, 
this  position  becomes  an  inseparable  characteristic  of  that  particular 
film,  and  controls  the  true  color  reproduction.  The  illustration 
shows  the  color  filter  (e,g,r)  placed  in  front  of  the  lens,  as  occurs  in 
practice.  Its  virtual  image  appears  at  a  distance  F  from  the  film, 
the  width  D  representing  the  limiting  diaphragm.  Each  of  the 
cylindrical  lenses  embossed  on  the  film  produces  a  real,  inverted, 
and  reduced  image  of  the  tri-color  filter  in  the  focal  plane  of  the 
embossed  lenses,  since  the  distance  from  the  film  to  the  filter,  in 
comparison  with  the  very  short  focal  length  of  the  embossed  lenses, 
is  practically  infinite.  The  filter  images  replace  the  grains  of  the 
mosaic  screen,  each  image  corresponding  to  one  of  the  previously 
mentioned  screen  units.  The  maximum  width  is  equal  to  the  width 
of  one  embossed  lens,  and  its  length  extends  over  the  entire  height 
of  each  picture,  in  the  direction  of  the  axis  of  the  cylindrical  lens. 
However,  the  units  do  not  carry  their  own  real  three-color  screens, 
but  look,  so  to  speak,  through  telescopes  to  the  one  common  color 
screen,  placed  in  the  limiting  diaphragm  of  the  lens.  The  film  itself 
appears  colorless  under  ordinary  observation. 

The  development  is  the  same  as  in  the  color  screen  process;  i.  e. 

April,  1933] 



the  original  must  be  developed  to  a  positive  in  order  to  obtain  a 
direct  reproduction  in  true  colors.  But  while  the  color  screen  positive 
itself  contains  all  colors,  it  is  necessary  to  provide  certain  optical 
arrangements  for  projecting  the  lenticular  films  in  true  colors. 
This  is  not  of  particular  advantage  in  motion  picture  work.  The 
simplest  arrangement  would  be  to  use  for  projection  the  same  lens 

FIG.  1.  Diagram  of  the  optical  system  of  the  Agfa- 
color  process.  The  cross-section  of  the  film  itself  is  shown 
at  a  much  greater  magnification  than  the  objective  and 

as  used  in  the  camera  which  would  simply  reverse  the  path  of  the 
exposing  light.  When  lenses  of  other  focal  length  and  construction 
are  used,  care  must  be  taken  that  the  position  and  width  of  the  color 
filter  appear,  from  the  point  of  view  of  the  lenticular  screen,  identical 
to  their  relations  during  exposure.  It  is  only  then  that,  at  the  given 
focal  length  of  the  lenticular  elements,  the  position  and  width  of  the 

306  F.  WEIL  [j.  s.  M.  P.  E. 

filter  images  behind  the  lenticular  screen  are  identical  to  those  of 
silver  images  formed  by  exposure  and  development  of  the  film. 

If  the  color  value  of  the  projected  image  is  to  be  at  its  best,  the 
screen  must  satisfy  certain  requirements : 

(1)  The  real  image  of  the  filter  as  projected  behind  the  lens  ele- 
ments must  lie  in  the  optical  plane  of  the  emulsion;    the  thickness 
of  the  film  base  and  the  focal  length  of  the  lens  elements  depend  on 
each  other.    The  focal  length  of  the  lenses,  in  turn,  depends  on  the 
refractive  index  of  the  base  and  on  the  curvature  of  the  lenses ;  hence 
the  embossing  of  the  screen  must  be  done  in  a  very  particular  way. 

(2)  The  real  filter  images  behind  the  screen  should  cover  the 
aperture  of  the  lens  element  in  the  same  way  as  the  filter  covers  the 
aperture  of  the  camera  lens.    No  light  should  be  allowed  to  pass  be- 
tween the  filter  images,  as  the  white  light  thus  passing  would  weaken 
the  color.    The  size  of  the  real  filter  image  behind  the  screen  is  de- 
termined by  the  following  simple  optical  relation:    If,  according  to 
Fig.  1,  D  is  the  apparent  width  of  the  filter,  as  viewed  from  the 
film,  and  F  is  the  apparent  distance  of  the  filter,  then  F/D  will  be  the 
aperture  at  which  the  filter  appears  when  viewed  from  the  film. 
If  we  call  F'  the  focal  length  of  the  screen  lenses,  d  the  width  of 
the  real  filter  image,  and  n  the  refractive  index  of  the  film  base,  the 
following  equation  will  result: 

?L     n  F 

If  the  ratio  F/D  is  given  by  the  focal  length  of  the  lens  and  the 
arrangement  of  the  filter,  then  the  maximum  focal  length  of  the  lens 
elements  is  limited,  as  the  width  of  the  filter  image  can  not  be  greater 
than  the  width  of  the  cylindrical  lens  elements;  or,  by  using  a  tri- 
color filter,  the  adjoining  images  on  the  outer  filter  strip  would  over- 
lap, and  red  and  blue  colors  would  appear  more  or  less  purple. 

(3)  The  narrower  the  individual  screen  lenses,  the  less  the  striped 
screen  of  the  image  will  be  visible  on  projection ;   on  the  other  hand, 
the  resolving  power  increases,  and  enables  even  the  smallest  images 
to  be  resolved  into  their  details.    Naturally,  the  grains  of  the  emul- 
sion should  be  small  compared  with  the  width  of  the  stripes  of  the 
filter  image.     In  the  Agfacolor  process,  in  which  the  width  of  the 
lenticular  elements  is  0.028  mm.,  the  images  of  the  individual  color 
stripes  have  a  maximum  width  of  0.009  mm.,  or  twenty  times  that  of 
the  wavelength  of  green  light.     With  respect  to  resolving  power, 
the  lenticular  screen  is  superior  to  the  mosaic  color  screen.     Owing 


to  the  geometrical  coordination  of  the  object,  lens,  screen,  and  image, 
details  even  smaller  than  the  width  of  the  lenses  are  reproduced  in 
their  correct  position  as  regards  color.  With  images  smaller  than 
one-thini  the  width  of  the  screen,  mixed  color  details  can  not  be 
resolved  into  their  individual  color  elements. 

(4)  The  quality  of  the  pictures  depends  largely  on  the  photo- 
graphic qualities  of  the  emulsion;  particularly,  on  its  color  sensi- 
tivity. The  latter,  in  turn,  determines  the  choice  of  the  filter  colors 
with  respect  to  their  spectral  transmission.  The  judgment  and 
decision  on  this  matter  and  the  choice  of  the  filter  combination 
must  be  based  merely  on  the  principles  of  subjective  psychology 
and  on  the  average  taste. 

Theoretically,  the  lenticular  films  can  be  printed,  but  not  by  the 
ordinary  contact  method — numerous  possibilities  of  doing  this 
have  been  described  and  patented.  It  is  important  to  preserve 
the  original  coordination  between  the  density  and  the  lens  elements. 
The  geometrical  coordination  between  the  silver  grain,  the  lens 
elements,  and  the  projection  lens  must  be  identical  in  both  the  copy 
and  the  original. 

From  the  above  it  is  seen  that  the  characteristics  of  the  lenticular 
film  depend  on  the  fact  that  the  film  itself  bears  the  optical  system 
that  makes  reproduction  in  colors  possible.  The  quality  of  the  pro- 
jected picture  depends  a  great  deal  on  the  degree  of  perfection  of  the 
screen.  Consequently,  processing,  storing,  and  projecting  require 
special  attention.  Grease  spots,  for  instance,  frequently  encountered 
in  motion  picture  theater  practice,  will  change  the  optical  properties 
of  the  screen  or  are  likely  to  cause  the  entire  screen  picture  to  dis- 

As  a  support  for  an  optical  system,  the  entire  area  of  the  film  must 
lie  in  proper  relation  to  the  lens  and  filter  in  both  exposure  and  pro- 
jection. Kinks  or  similar  mechanical  defects  cause  color  distortions 
in  projection.  In  addition  to  this,  an  exact  adjustment  of  the  camera 
or  projection  lens  with  regard  to  the  film  is  very  necessary.  If,  for 
instance,  the  projector  aperture  is  not  vertical  to  the  optical  axis 
of  the  lens,  or  if  the  film  does  not  lie  flat  in  the  projector  aperture, 
untrue  colors  will  appear  at  the  edges — so-called  color  dominants. 
Excessive  drying  of  the  film,  which  always  causes  some  loss  of  sol- 
vents, also  causes  some  displacement  of  the  lens  elements  and  is 
likely  to  disturb  the  projection.  It  is,  therefore,  advisable  alway 
to  store  the  film  in  air-tight  cans. 

308  F.  WEIL 

With  regard  to  transmission  of  light  by  the  lenticular  optical 
system,  since  the  tri-color  analysis  is  made  with  only  one  lens  (for 
instance,  a  red  surface  would,  when  exposed  and  projected,  use  only 
one- third  of  the  aperture;  and,  since  the  colors  of  the  filters  are  not 
pure  spectral  colors,  but  contain  some  gray),  there  is  greater  loss 
of  light  in  this  process  than  in  ordinary  black-and-white  photog- 
raphy. However,  in  motion  picture  photography,  using  lenses  of 
short  focal  length  and  greater  depth  of  focus,  larger  apertures  can 
be  used.  The  maximum  usable  width  of  the  aperture  is  limited  by 
the  effective  area  of  the  lens  in  which  there  is  no  vignetting.  If  the 
filter  were  larger,  parts  of  the  lens  mounting,  or  their  virtual  images, 
would  obscure  portions  of  the  filter.  This  partial  loss  of  one  color 
would  cause  color  dominants  to  appear  at  the  edges  of  the  picture 
when  projected.  For  the  same  reason,  it  is  impossible  to  use  an 
iris  diaphragm  in  order  to  reduce  the  amount  of  light.  It  is  necessary 
to  use  neutral  density  filters  (Eastman)  or  detachable  slit  diaphragms 
(Agfa).  For  exposure,  lenses  with  relative  apertures  less  than 
//2.0  are  hardly  to  be  considered.  The  loss  of  light  caused  by  the 
optical  system  can,  to  a  certain  degree,  be  compensated  for  by  in- 
creasing the  photographic  sensitivity  of  the  film.  As  the  situation  is 
at  present,  lenticular  film  can  be  used  for  outdoor  exposures  even  under 
an  overcast  sky,  and,  under  favorable  lighting  conditions,  indoors. 

Satisfactory  projection  can  be  obtained  only  with  powerful  pro- 
jectors. Because  of  the  loss  of  light,  mentioned  before,  and  for 
psychological  reasons,  it  is  necessary  to  have  maximum  brightness 
for  color  projection. 

Before  lenticular  film  can  be  introduced  into  motion  picture 
theaters,  some  technical  (not  fundamental)  difficulties  must  be 
overcome.  First,  it  must  be  possible  to  make  prints;  second,  the 
screen  brightness  must  be  sufficient.  The  requirements  regarding 
illumination  in  the  studio  can  be  satisfied  by  increasing  the  sensitivity 
of  the  photographic  emulsion.  It  is,  however,  difficult  to  solve  the 
problem  of  obtaining  satisfactory  illumination  on  the  large  screens 
used  in  motion  picture  theaters. 


1  EGGERT,  J.:     "A  Resume  of  the  Status  of  Color  Cinematography,"    VIII. 
Internat.  Kongress  fur  wissenschaftliche  und  angewandte  Photographic,  /.  A. 
Barth,  Leipzig,  1932,  p.  214. 

2  BAKER,  T.  THORNE:     "The  Spicer-Dufay  Process  of  Color  Cinematography," 
VIII.     Internat.  Kongress  fur  wissenschaftliche  und  angewandte  Photographic, 
/.  A.  Barth,  Leipzig,  1932,  p.  230. 


Summary — This  paper  describes  the  general  procedure  employed  in  producing 
animated  cartoons,  particularly  the  technic  employed  by  the  Walt  Disney  Studios. 
The  qualities  required  in  the  animators,  and  the  problems  that  these  animators  must 
solve  in  realizing  the  dramatic  situations  and  synchronizing  them  with  the  music 
and  sound  effects  are  discussed.  An  example  of  the  procedure  followed  in  producing 
the  cartoon  is  given,  including  illustrations  of  the  layout  sheet,  exposure  sheet,  and 
camera  field  charts. 

The  method  followed  in  producing  a  sound  cartoon  is  basically 
simple.  The  degree  of  its  success  depends  almost  entirely  upon  the 
care  and  attention  given  to  detail.  The  picture  is  built  up  frame  by 
frame,  and  any  tendency  to  overlook  detail  is  reflected  in  the  finished 
product.  When  one  realizes  that  ten  to  fifteen  thousand  individual 
drawings  are  required  for  each  complete  production,  it  becomes  clear 
why  such  great  care  must  be  exercised  by  all  the  production  de- 

This  company  produces  two  series  of  cartoons,  the  Mickey  Mouse 
and  the  Silly  Symphonies.  This  year,  the  program  calls  for  the 
production  of  a  total  of  twenty-six  cartoons,  eighteen  of  which  are  to 
be  Mickey  Mouse,  and  eight  Silly  Symphonies.  All  the  Silly  Sym- 
phonies are  to  be  released  in  "Technicolor." 

In  the  Mickey  Mouse  cartoons,  it  has  been  the  endeavor  to  build 
up  definite  personalities,  not  only  of  Mickey  and  Minnie,  but  of 
all  the  supporting  characters  as  well.  Every  effort  is  made  to  main- 
tain the  same  personality  of  each  character  in  each  picture,  so  as  to 
establish  that  character  in  the  mind  of  the  public. 

The  Silly  Symphonies  are  entirely  free  from  any  such  limitation, 
and  wide  latitude  is  possible  in  selecting  the  subjects.  It  is  the 
present  intent  to  maintain  this  series  in  the  realm  of  the  unreal. 
The  spirit  of  the  seasons  has  been  expressed  in  the  subjects  entitled 

*  Presented  at  a  meeting  of  the  Pacific  Coast  Section,  Dec.  14,  1932. 
**  Walt  Disney  Studios,  Hollywood,  Calif. 


310  WILLIAM  GARITY  [j.  s.  M.  P.  E. 

Springtime,  Summer,  Autumn,  and  Winter;  in  others,  the  themes 
have  been  drawn  from  the  fairy  tales  of  old. 

The  principal  difference  between  producing  live-action  subjects 
and  animated  cartoons  lies  in  the  fact  that  in  live  action,  it  is  possible 
to  rehearse  the  characters,  see  the  immediate  results,  and  select  the 
best  of  several  takes  for  the  final  product.  In  producing  a  cartoon, 
the  director  must  visualize  his  action  in  terms  of  pen  lines,  plan  his 
entire  continuity,  entrances  and  exits,  dissolves  and  cuts;  in  other 
words,  do  all  his  editing,  before  a  single  picture  is  drawn.  His  only 
recourse,  when  his  picture  is  finished,  is  to  eliminate  scenes.  But  it  is 
not  always  possible  to  do  this,  because  a  recorded  musical  score  is 
not  as  flexible  as  we  sometimes  wish  it  were. 

In  producing  cartoons,  it  is  necessary  to  analyze  the  story  and 
break  it  down  into  several  scenes,  and  to  distribute  these  scenes 
among  many  individual  animators.  This  requires  that  all  the  artists 
adopt  a  standard  style  of  drawing,  a  difficult  matter  for  an  artist 
when  he  is  entering  the  cartoon  business.  He  must  change  his  style 
to  conform  to  the  requirements  of  production.  This  is  particularly 
difficult  for  an  artist  who  has  been  developing  his  own  individual 
style  for  any  length  of  time. 

Three  types  of  men  to  be  found  in  the  cartoon  business  are:  the 
artist,  the  animator,  and  the  artist-animator.  There  are  many  men 
of  artistic  ability  who  find  it  impossible  to  create  animated  cartoons. 
There  are  also  those  who  can  animate,  who  can  produce  good  action, 
but  whose  artistic  ability  is  mediocre.  The  third  group  comprises 
the  artist-animators,  who  combine  the  qualities  of  the  other  two 

Experienced  men  in  this  field  are  few  and  it  is  necessary,  therefore, 
to  maintain  a  group  of  apprentices  of  little  or  no  production  value, 
and  to  train  them  in  the  art  of  animation  so  as  to  be  able  to  develop 
the  organization.  These  apprentices  are  required  to  attend  art 
classes  at  the  studio.  The  period  of  apprenticeship  lasts  for  about 
six  months,  never  less,  and  often  longer. 

Very  few  men  qualify  in  all  branches  of  art.  Some  excel  in  char- 
acterization; others  in  mechanical  action;  others  are  particularly 
gifted  in  animating  dialog;  others  have  the  ability  to  give  subtle 
touches  to  action.  They  are  all  classified  as  to  their  ability,  and 
as  far  as  possible,  are  given  those  parts  of  the  work  for  which  their 
particular  talents  are  best  adapted.  Considering  the  fact  that  an 
artist-animator  can  with  diligence  produce  only  five  feet  of  action 

April,  1933]  ANIMATED  CARTOONS  311 

every  eight  hours,  it  is  necessary  to  conserve  his  time  by  assigning 
to  him  the  kind  of  work  he  is  able  to  do  best. 

In  producing  a  cartoon,  the  first  consideration  is  the  story.  If 
the  story  is  good  the  results  are  usually  gratifying.  The  finest 
music,  the  best  sound  recording  and  the  most  expert  camera  work, 
will  never  make  a  success  of  a  cartoon  with  a  poor  story.  As  in  live 
action,  the  director  plays  an  important  part  in  cartoon  production. 
It  is  his  function  to  present  the  story  so  as  to  make  the  most  of  its 
strong  points  and  bolster  the  weak  ones.  He  must  visualize  the 
action,  build  up  the  situations,  and  time  the  action  so  that  nothing 
is  lost.  The  selection  of  music  and  sound  effects  is  his  responsi- 
bility; and  he  must  supervise  the  work  of  each  animator  in  order 
that  his  ideas  be  carried  out,  in  addition  to  supervising  the  recording 
of  the  music  and  effects.  On  him,  as  in  live  action,  rests  the  responsi- 
bility of  the  picture  as  a  whole.  Next  in  importance  are  gags  and 

Following  in  the  order  of  importance,  are  the  musical  score  and 
sound  effects.  The  music  must  fit  the  mood  of  the  picture  in  order  to 
be  effective:  if  properly  chosen,  it  enhances  the  value  of  the  story 
and  the  action;  if  improperly  handled,  it  annoys  and  detracts. 
In  the  same  way,  certain  sounds  are  effective  in  some  situations, 
whereas  the  same  sound  in  a  different  situation  would  be  discordant 
and  annoying.  Sound  effects  should  be  adapted  to  the  action; 
a  sound  effect  should  never  be  used  unless  the  eye  is  conscious  of  the 
source  of  the  sound. 

The  last  items  in  consideration  of  a  good  subject  are  technical 
perfection,  camera  work,  and  sound  quality.  While  we  place  these 
items  last  in  importance,  they  are  the  ones  that  cause  us  the  greatest 
trouble  and  require  constant  supervision. 

The  synchronization  of  sound  to  the  cartoon  is  probably  responsi- 
ble, to  some  degree  at  least,  for  their  success  in  the  field.  This  one 
phase  of  producing  cartoons  is  probably  the  least  understood  by  the 
public,  although  it  is  perhaps  the  simplest  part  of  the  problem. 
Since  the  advent  of  talking  pictures  and  the  standardization  of  film 
speed,  the  problem  became  simply  one  of  resolving  all  musical 
tempos  in  terms  of  the  standard  speed,  and  of  making  a  consecutive 
series  of  drawings  to  fit  this  tempo.  In  order  to  do  this,  certain 
basic  tempos,  multiples  of  the  frame  speed  of  the  film,  have  been 
established.  For  example,  the  fastest  tempo  employed  is  one  beat 
every  six  frames,  amounting  to  four  beats  per  second.  The  total 

312  WILLIAM  GARITY  [j.  s.  M.  P.  E. 

range  is  from  this  to  one  beat  every  twenty  frames,  or  one  beat  every 
Veths  of  a  second. 

The  Story  Department  presents  the  most  difficult  of  all  the  pro- 
duction problems.  When  one  realizes  that  a  picture  must  be  re- 
leased every  fourteen  days,  the  reason  is  quite  obvious.  The  men  in 
this  department  work  continuously,  developing  material  for  pictures. 
The  first  step  in  the  production  of  a  cartoon  takes  the  form  of  a  rough 
draft  of  a  story  prepared  by  the  Story  Department.  The  following 
is  an  abstract  of  such  a  story  outline  : 

United  Artists  Symphony  No.  7,  Santa's  Workshop;  Jackson,  director;  Church- 
ill, music. 

Story  opens  showing  exterior  of  Santa's  workshop  at  the  North  Pole — beautiful 
scene,  snow  falling,  etc.,  Santa's  factory  buildings. 

Dissolve  into  an  exterior  of  Santa's  stables;  little  gnomes  busily  grooming  the 
reindeer,  washing  their  teeth,  etc.;  all  busy  and  whistling,  or  some  other  musical 

This  dissolves  to  the  interior  of  the  workshop,  showing  happy  gnomes  busily 
operating  the  quaint  machinery ;  all  gnomes  whistle  as  they  work.  Show  various 
closeups  of  individual  elves  making  toys.  Everything  is  run  in  the  manner  of  the 
Ford  factory.  (Plenty  of  opportunities  here  for  showing  the  ludicrous  methods 
used  by  the  gnomes  in  making  the  toys.) 

Santa  is  the  big  boss  who  "okays"  all  the  toys.  He  is  happy  and  very  good 
natured,  and  gets  a  big  kick  out  of  the  various  things  the  toys  do.  Santa  could 
teach  the  dolls  to  speak  and  say  "mama." 

Amusing  action  of  toys  of  various  kinds,  walking  in  their  own  individual  ways. 
The  toy  band  strikes  up  a  snappy  march  and  all  join  in  a  big  procession  leading 
to  Santa's  bag.  When  all  the  toys  enter  the  bag,  Santa  picks  it  up,  puts  it  into  his 
sleigh,  and  drives  off.  Make  a  beautiful  final  scene,  Santa  disappearing  in  the 
sky  in  the  distance,  all  the  elves  singing  a  Christmas  song;  just  before  the  iris 
closes,  show  a  silhouette  effect  of  his  reindeer  and  sleigh  as  they  cross  the  Christ- 
mas moon,  the  voices  of  the  elves  coming  in  full  volume  for  a  final  finish  effect 
on  the  end  title. 

Everyone  think  this  over  and  have  some  good  "gags"  ready  to  hand  in  at  the 
next  gag  meeting.  I  expect  a  big  turnout  on  this  story.  "Walt." 

This  story  outline  is  mimeographed  and  handed  to  all  the  ani- 
mators at  a  gag  meeting.  These  gag  meetings  are  held  every  two 
weeks  for  the  purpose  of  discussing  future  pictures.  The  discussion 
is  held  within  the  limits  set  by  the  Story  Department,  outlined  as 
above.  Two  weeks  following  the  discussion  of  the  story,  the  ani- 
mators hand  to  the  Story  Department  suggested  gags  and  situations 
for  the  particular  story.  The  Story  Department  then  makes  a 
complete  study  of  the  submitted  gags  and  situations,  and  prepares  a 
definite  story  outline  in  the  form  of  a  scenario.  Then  a  conference 

April,  1933] 



is  held  with  the  director  and  the  musician,  who  are  to  produce  the 
picture,  at  which  the  director  is  made  acquainted  with  the  story 
and  assisted  in  preparing  the  continuity  so  as  to  preserve  the  original 
ideas  and  situations. 

In  this  conference  is  included  the  "set  designer,"  known  as  the 
"layout  man."  It  is  his  function  to  prepare  rough  sketches  of  the 
complete  scenes,  depicting  the  atmosphere  of  the  action,  keeping 
in  mind  the  movement  of  the  characters.  From  these  sketches,  the 
background  sketches  are  prepared  and,  finally,  the  finished  back- 
grounds. In  making  the  backgrounds,  it  is  necessary  to  leave  clear 

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FIG.  1.     Layout  sheet  used  for  planning  the  picture. 

such  portions  as  will  later  be  occupied  by  the  animated  figures. 
The  layout  man  must  assist  the  director  in  maintaining  good  con- 
tinuity of  background,  so  that  when  camera  angles  are  changed, 
the  resulting  background  change  will  be  smooth. 

The  director  and  the  musician,  at  the  end  of  this  conference, 
have  a  very  definite  idea  of  the  story,  situations,  and  gags  to  be 
used;  and  the  approximate  footage  of  film  that  will  be  needed. 
The  story  is  then  laid  out  on  a  layout  sheet,  shown  in  Fig.  1.  Each 
"box"  (or  small  rectangle)  represents  a  bar  of  music.  How  much  of 
the  picture  is  to  be  shown  during  each  bar  depends  on  the  tempo 



[J.  S.  M.  P.  E. 

at  which  the  music  is  to  be  played.  Referring  to  Fig.  1,  each  box, 
starting  at  1,  covers  48  frames  of  action,  the  tempo  being  indicated 
as  4-12.  While  working  on  the  sheet,  the  musical  director  writes 
his  preliminary  master  score.  In  some  cases,  when  it  is  desired  to  use 
a  certain  piece  of  music,  the  director  is  required  to  adapt  the  action 
to  the  music.  At  other  times,  the  action  requires  entire  freedom 
from  musical  limitations,  except  with  respect  to  tempo.  In  this 
case,  the  musician  must  compose  music  to  suit  the  action.  It  is  by 
means  of  the  layout  sheet  that  the  entire  problem  is  resolved,  the 
action  made  to  suit  the  music,  and  the  music  written  to  suit  the  action. 





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M.L.S.      BAND    AND    SOLDIERS    KARCH. 




M.C.U.      VARIOUS 




M.L.S.      TOYS   START    INTO  BAG    (TRUCK) 

FIG.  2.     A  production  schedule. 

The  director  and  the  musician  work  hand  in  hand,  measure  by 
measure,  frame  by  frame;  each  one  trying  to  adjust  his  particular 
problem  to  meet  the  demands  of  the  story. 

When  the  layout  sheet  is  completed,  the  director  has  his  picture 
completely  laid  out  to  the  frame,  and  the  musician  his  master  score 
to  the  note.  Slight  changes  may  later  be  made  in  order  to  accommo- 
date the  exigencies  that  may  arise  when  the  pictures  are  animated. 
It  is  everyone's  desire  to  preserve  the  layout  sheet  as  final,  but 
necessity  requires  that  it  remain  flexible. 

The  production  schedule  shown  in  Fig.  2  is  next  prepared.  As 
will  be  noted,  this  schedule  contains  the  scene  numbers,  the  footage 

April,  1933] 



of  the  scene,  the  name  of  the  artist,  and  a  description  of  the  action  to 
take  place :  scene  24,  the  first  scene  on  the  sheet,  is  allocated  a  footage 
of  14  feet,  10  frames  to  be  drawn  by  the  artist,  Ben,  and  to  be  a 
medium  close-up  showing  a  permanent  wave.  As  soon  as  the  schedule 
is  completed,  the  director  fills  out  an  exposure  sheet,  shown  in  Fig.  3, 
describing  in  terms  of  frames  of  picture  the  continuity  of  the  action, 
exactly  on  what  frame  the  sound  effects  will  occur,  and  what  the 
nature  of  the  sound  will  be.  The  tempo  of  the  action  is  also  shown  on 




U.S  '7 



PAN      • 
TO    H 

PER   X 




FIG.  3.     Exposure  sheet  completely  filled  out,  showing  instructions 
for  cameraman. 

the  exposure  sheet.  This  exposure  sheet  is  prepared  with  the  assis- 
tance of  the  musician,  who  simultaneously  marks  on  his  master  music 
score  the  exact  position  of  sound  effects. 

The  director,  when  preparing  the  exposure  sheet,  definitely  in- 
structs the  animator  as  to  the  nature  of  the  scene  to  be  depicted, 
the  exact  footage  that  the  scene  should  occupy,  and  the  tempo  of  the 
music  to  be  played  during  that  particular  sequence.  The  director 
also  explains  to  the  animator  in  great  detail  the  relation  of  his  se- 
quence to  the  rest  of  the  story,  points  out  the  particular  gags  or 
situations  that  are  to  be  developed,  and  supplies  the  animator 

316  WILLIAM  GARITY  [j.  s.  M.  P.  E. 

with  the  necessary  information  concerning  the  preceding  and  suc- 
ceeding scenes.  The  animator  is  also  furnished  with  a  background 
sketch  which  serves  as  his  stage  setting.  It  is  the  animator's  function 
to  visualize  the  scene  in  terms  of  pen-and-ink  lines,  and  to  produce  a 
series  of  progressive  drawings  of  the  scene  that  will  tell  the  story 
and  the  ideas  incidental  to  it.  The  animator  is  quite  limited,  due 
to  the  fact  that  the  musical  tempo,  as  well  as  the  footage  of  the 
scene,  is  fixed.  He  will  sometimes  find  it  necessary  to  shorten  or  to 
extend  his  bit  of  action  to  complete  his  sequences  more  effectively. 
In  this  case,  he  confers  with  the  director;  and  if  the  latter  approve 
such  a  change,  the  musician  is  consulted,  who  must  rearrange  the 
score  to  suit  the  change  of  footage.  Such  a  procedure  is  avoided 
as  much  as  possible,  for  obvious  reasons. 

As  the  animator  makes  his  progressive  drawings,  he  numbers 
them  serially,  recording  them  at  the  same  time  in  the  columns  pro- 
vided on  the  exposure  sheet,  in  the  order  in  which  they  are  later  to 
be  photographed.  The  animator  confines  his  drawings  to  a  field 
approximately  seven  by  nine  inches.  At  the  lower  edge  of  the  drawing 
paper  outside  the  field  are  two  perforated  holes.  These  control 
the  registration  of  the  drawings.  The  animator's  drawing  board  is 
provided  with  an  insert  of  glass,  under  which  is  placed  an  electric 
light.  On  the  edge  of  the  glass  insert  nearest  the  animator,  on  the 
top  surface  of  the  drawing  board,  is  placed  a  bar  containing  the 
registering  pins,  on  which  the  paper  is  fastened.  All  drawings,  in- 
cluding backgrounds,  are  made  only  when  the  paper  is  engaged  by 
these  pins.  The  paper  used  has  a  hard  finish,  and  is  very  light  in 
weight,  so  that  tracing  of  images  is  facilitated. 

Each  animator  has  an  "in-between"  man  or  an  assistant,  and 
generally  two  apprentices.  In  order  to  conserve  the  animator's 
time,  he  makes  drawings  of  only  the  extreme  action,  and  makes  a 
finished  model  as  a  guide  for  his  assistants,  who  fill  in  the  intervening 
drawings.  For  example:  if  the  action  require  a  walking  character, 
taking  16  frames  for  a  complete  step,  the  animator  makes  drawings 
Nos.  1,  8,  and  15,  his  assistant,  or  in-between  man,  making  drawings 
Nos.  2  to  7,  inclusive,  and  9  to  14,  inclusive.  The  assistant  then  hands 
the  drawings  to  the  apprentices,  who  fill  in  all  the  necessary  detail. 

When  the  animator  has  completed  his  particular  scene,  the 
drawings  are  turned  over  to  the  Inking  and  Painting  Department, 
the  function  of  which  is  to  transfer  or  trace  each  drawing  on  celluloid 
sheets.  These  celluloid  sheets  are  the  approximate  size  of  the  paper, 

April,  1933]  ANIMATED  CARTOONS  317 

and  about  5/i0ooths  of  an  inch  in  thickness.  They  are  perforated  with 
registering  holes,  identical  to  those  in  the  drawing  paper.  The  paper 
drawings  are  placed  on  the  registering  pins,  the  celluloid  sheet  is 
superimposed  on  the  drawing,  and  a  very  careful  tracing  of  the  draw- 
ing is  made  with  black  India  ink.  After  the  tracing  of  the  outline 
has  dried,  the  celluloid  is  reversed,  and  the  entire  area  occupied  by 
the  figures  on  the  drawings  is  made  opaque  with  paint. 

The  primary  reason  for  using  celluloids  is  an  economic  one.  If 
the  transparency  were  not  used,  it  would  be  necessary  to  draw  a 
complete  background  for  each  frame  of  the  picture,  which,  of  course, 
would  be  an  economic  impossibility.  To  avoid  doing  this,  a  single 
background  is  drawn,  the  characters  working  against  this  background 
being  traced  on  the  celluloid  sheets.  As  the  entire  area  occupied  by 
the  character  is  rendered  opaque,  the  background  is  completely 
matted  out  by  the  character  when  the  celluloid  sheets,  inked  and 
painted,  are  superimposed  on  the  background.  It  is  possible  to 
have  a  large  number  of  characters,  each  doing  something  different, 
by  tracing  each  character  on  a  separate  sheet  of  celluloid,  and  simul- 
taneously superimposing  these  celluloid  sheets  upon  the  background. 
The  use  of  many  such  celluloid  sheets  aggravates  the  photographic 
problems,  due  to  the  light  losses  and  color  changes  introduced  by  the 
celluloid.  Four  sheets  seem  to  be  the  greatest  number  that  may  be 
used  without  seriously  affecting  the  photography. 

For  rendering  the  celluloid  sheets  opaque,  white,  black,  and 
five  shades  of  gray  paint  are  used.  When  a  number  of  characters  are 
superimposed  simultaneously  on  the  background,  1,  2,  3,  or  4  sheets 
of  celluloid  are  used.  In  order  to  produce  the  same  color  value  in  the 
negative,  five  different  shades  of  gray  paint  must  be  employed. 
The  darkest  shade  is  used  on  the  top  sheet  and  the  lightest  on  the 
background.  This  is  necessary  because  of  transmission  losses  inherent 
to  the  celluloid.  The  thickness  of  the  sheet  is  also  a  factor  to  be  con- 
sidered; and  for  that  reason  all  sheets  are  carefully  graded  as  to 
thickness  and  color,  in  order  to  minimize  the  painting  problems  and 
reduce  density  changes  in  the  half-tones  of  the  film. 

After  the  picture  is  photographed,  all  traces  of  the  ink  lines  and 
of  the  paint  are  removed  by  washing,  thus  reclaiming  the  sheets  for 
later  use.  In  practice,  the  celluloid  sheets  are  never  used  more  than 
three  times,  due  to  the  fact  that  the  surfaces  become  badly  scratched 
and  marred  when  used  more  often.  Also,  after  the  third  time,  the 
celluloid  becomes  discolored,  an  effect  impossible  to  control  by 



[J.  S.  M.  P.  E. 

means  of  the  paint.  Also,  as  the  celluloid  ages,  shrinkage  becomes  a 
serious  factor,  preventing  the  sheets  from  fitting  properly  over  the 
registering  pins. 

After  the  celluloid  sheets  are  completed  by  the  Painting  Depart- 
ment, they  are  turned  over  to  the  Camera  Department  for  photo- 
graphing. A  standard  Bell  &  Howell  camera  is  employed,  equipped 
with  a  stop-motion  mechanism  driven  by  a  synchronous  motor. 
The  camera  can  be  moved  vertically  to  change  the  size  of  the  field, 
as  well  as  from  right  to  left  (east  and  west),  fore  and  aft  (north  and 

FIG.  4.     Camera  field  chart;     used  for  orienting  the  optical  center  of  the 


south),  and  rotated  through  an  arc  of  360  degrees.  The  optical  center 
of  the  camera  is  oriented  by  means  of  a  "camera  field  chart,"  shown  in 
Fig.  4.  A  copy  of  this  chart  is  in  the  hands  of  each  animator.  The 
calibration  of  this  chart  is  identical  to  that  of  the  scales  on  the  camera. 
Fig.  5  shows  a  photograph  of  the  cartoon  camera  and  camera  stand. 

The  celluloid  sheets  representing  the  action  of  a  single  frame 
of  the  picture  are  assembled  and  placed  over  the  background  of  the 
scene.  The  "eels"  are  held  in  position  by  registering  p'ins.  An 
optical  glass  plate  flattens  the  "eels"  against  the  background,  thus 

April,  1933] 



removing  any  wrinkles  or  curl.     The  glass  plate  is  operated  by  a 
compressed  air  mechanism. 

If  less  than  four  "eels"  are  required  for  the  action,  blank  "eels" 
are  added  so  as  to  preserve  the  photographic  values  of  the  back- 
ground. Four  "eels"  are  always  used  between  the  camera  and  the 
background.  The  camera  operator  follows  the  instructions  outlined 
on  the  exposure  sheet.  A  completed  exposure  sheet  is  shown  in  Fig.  3. 

FIG.  5.     Cartoon  camera  in  camera  stand. 

Approximately  100  hours  are  required  to  photograph  a  cartoon 
subject,  which  averages  about  600  feet  of  film.  If  the  subject  should 
contain  more  than  the  usual  number  of  so-called  "trick"  shots, 
which  may  require  complete  camera  readjustment  for  each  frame  of 
film,  the  shooting  time  will  easily  run  from  125  to  150  hours. 

During   the   time   consumed   in   animating,    inking,    and   photo- 



[J.  S.  M.  P.  E. 

graphing  the  picture,  the  musical  score  is  completed  and  arranged, 
and  the  sound  record  is  made.  It  is  not  necessary  for  the  purpose  of 
scoring  to  see  the  picture.  As  the  musical  score  is  prepared  in  ac- 
cordance with  the  same  tempos  as  those  used  in  drawing  the  pictures, 
the  musical  director  knows  exactly  at  what  frame  in  the  picture 
every  musical  note  or  sound  effect  will  occur. 

Not  only  are  parts  written  for  all  the  instruments  in  the  orchestra, 

FIG.  6.     Recording  a  Mickey  Mouse  cartoon;  trap  drummer's  table  in  center. 
Note  the  head-phones  used  by  each  member  of  the  orchestra. 

but  each  trap  drummer,  or  effect  man,  is  supplied  with  a  score  that  is 
as  complete  in  detail  as  is  the  part  for  the  first  violin.  The  position 
of  the  effects  is  written  on  the  score  as  musical  notes,  postscripts 
being  added  to  describe  the  kind  of  sound  or  effect  required.  The 
trap  drummer  must  be  able  to  read  music  and  to  assign  proper 
values  to  the  sounds  as  indicated  by  the  musical  notations. 

Each  member  of  the  orchestra,  as  well  as  the  conductor,  is  provided 
with  a  head-phone  (see  Fig.  6)  similar  to  that  used  by  telephone 
operators,  in  which  is  heard  the  tempo  of  the  music  to  be  played. 
This  beat  is  developed  by  means  of  an  audio -frequency  oscillator 

April,  1933]  ANIMATED  CARTOONS  321 

controlled  by  a  synchronously  driven  contacting  device,  which  makes 
and  breaks  contacts  in  terms  of  frames  of  synchronously  running 
film.  Experience  has  shown,  after  trying  perhaps  every  known 
method  of  achieving  perfect  synchronism,  that  the  aural  process 
thus  employed  is  as  nearly  fool-proof  as  any  system  could  be.  The 
Disney  Studios  were  probably  the  first  to  synchronize  cartoons  by 
projecting  a  wavy  line  to  be  used  as  a  tempo  guide,  or  the  use  of  the 
bouncing  ball.  These  two  methods  were  abandoned,  after  a  brief 
trial,  in  favor  of  the  present  method.  For  scoring  the  cartoons,  there 
are  employed  an  orchestra  ranging  from  twelve  to  twenty  musicians 
and  four,  and  sometimes  five,  effect  men  for  producing  sound  effects, 
in  addition  to  the  vocal  artists.  To  synchronize  the  orchestra  is 
relatively  easy;  the  greater  problem  is  to  synchronize  effects,  be- 
cause of  their  unmusical  character  and  irregular  occurrence.  The 
effect  man  has  quite  a  problem,  as  he  sometimes  has  on  his  table 
dozens  of  sound  producing  devices,  which  he  must  pick  up  and 
operate  at  very  definite  places  in  the  score.  With  the  aural  method 
of  controlling  synchronism,  he  is  constantly  aware  of  the  tempo, 
and  his  attention  can  be  concentrated  on  his  musical  score  and 
effects.  It  is  not  necessary  for  him  even  to  follow  the  lead  of  the 
conductor,  except  at  the  start.  The  actual  recording  technic  is 
approximately  the  same  as  used  to  record  any  orchestra. 

To  facilitate  cutting  the  sound  track,  acoustical  beats  are  recorded 
at  the  beginning  and  at  the'  end  of  the  take.  These  beats  are  con- 
trolled by  the  musical  director.  A  predetermined  number  of  beats 
are  produced  in  synchronism  with  the  controlling  tempo,  followed 
by  a  predetermined  time  interval  in  which  no  sound  occurs,  pre- 
ceding the  first  bar  of  the  music.  This  enables  the  cutter  to  deter- 
mine, with  absolute  accuracy,  the  exact  start  of  the  sound  take. 
It  is  quite  possible,  and  has  been  the  practice  of  this  studio,  to  as- 
semble the  sound  track  from  these  visible  indications  on  the  film, 
assemble  the  picture  negative  from  the  exposure  sheets,  attach 
academy  trailers,  and  make  a  composite  print.  Errors  in  the  syn- 
chronism are  due  to  errors  in  supervision. 

The  dialog  is  handled  in  a  somewhat  different  manner.  In  the 
case  of  dialog  that  does  not  follow  the  tempo  of  the  music,  prescoring 
is  necessary:  the  dialog  is  recorded  before  drawings  of  the  subject 
are  made.  The  recorded  sound  track  is  sent  to  the  Cutting  De- 
partment, where  a  careful  analysis  of  the  position  on  the  film  and  of 
the  various  speech  components  is  made;  such  components  being 


translated  into  terms  of  frames  on  an  exposure  sheet.  The  exposure 
sheet  then  indicates  to  the  animator  the  exact  position  of  each  and 
every  syllable  in  the  dialog  and  the  drawings  are  made  to  fit  the 
particular  conditions.  In  the  case  of  musical  or  rhythmical  dialog, 
it  is  possible  for  the  animator  to  make  suitable  drawings  for  the 
words  to  be  used,  and  in  this  case  the  dialog  is  recorded  at  the  time 
the  orchestral  recording  is  made.  This  form  of  dialog  is  one  to 
be  avoided,  as  in  the  finished  product  the  composite  result  sometimes 
lacks  realism;  whereas  in  the  first  method  of  prescoring,  it  is  quite 
possible  to  make  the  audience  feel  that  the  cartoon  character  is 
actually  talking. 



Summary. — A  method  of  measuring  axial  chromatic  aberration  is  described  in 
which  an  image  of  a  line  grating  test  object  illuminated  by  a  monochromator  is  formed 
by  the  lens  under  test.  The  image  thus  formed  is  projected  onto  a  steeply  inclined 
photographic  plate  by  means  of  a  highly  corrected  microscope  objective.  Individual 
exposures  are  made  at  selected  wavelengths  and  a  curve  showing  the  change  of  image 
position  as  a  function  of  wavelength  for  the  lens  under  test  is  readily  derived  from 
measurement  of  the  developed  plate.  Data  are  given  showing  the  order  of  agreement 
attained  between  computed  values  of  axial  chromatic  aberration  and  values  obtained 
by  this  method. 

No  commercially  available  photographic  lens  offers  perfect  defi- 
nition over  an  extended  field  because  of  the  influence  of  inherent 
aberrations.  The  aberrations  are  usually  so  distributed  as  to  result 
in  the  best  possible  average  definition  over  the  required  picture  area. 
In  general,  such  a  lens  is  of  high  relative  aperture  and  is  intended 
for  use  with  an  object  distance  that  is  many  times  its  focal  length. 
Commercial  considerations  have4,  in  certain  cases,  led  to  the  develop- 
ment of  special  types  of  lens  systems  where  the  lens  designer  has  been 
able  to  meet  requirements  imposed  by  special  needs.  The  process 
lens  is  illustrative  of  this  type.  In  this  case,  corrections  are  effected 
at  a  low  relative  aperture  for  a  magnification  of  approximately  unity, 
and  particular  care  is  given  to  the  correction  of  lateral  chromatism  as 
this  aberration  would  obviously  prohibit  precise  registry  of  negatives 
made  through  trichromatic  filters. 

Many  physical  instruments  are  now  in  use  in  which  photographic 
methods  are  employed  to  record  a  wide  variety  of  transient  phe- 
nomena. The  modern  high-speed  oscillograph  is  representative  of 
this  type  of  instrument;  and  such  instruments,  in  general,  employ 
a  lens  system  as  a  means  of  imaging  an  aperture  on  the  plane  oc- 

*  Published  by  permission  of  the  Optical  Society  of  America;    Mr.  Herriott's 
paper  appears  simultaneously  in  /.  Opt.  Soc.  Amer.,  22  (April,  1933),  No.  4. 
**  Bell  Telephone  Laboratories,  New  York,  N.  Y. 


324  W.  HERRIOTT  [j.  s.  M.  P.  E. 

cupied  by  the  light-sensitive  material.  Such  imagery  may  be  effected 
under  a  wide  variety  of  conditions  for  which  certain  optical  factors 
may  not  receive  proper  design  consideration.  Such  factors  involve 
the  brightness  and  energy  distribution  of  the  light  source,  the  mag- 
nification adopted,  and  particularly  the  extent  of  the  angular  field 
required.  Factors  relating  to  photographic  materials,  such  as  re- 
solving power,  spectral  sensitivity,  contrast,  and  speed,  are  of  equal 
importance.  We  frequently  observe  instances  where  commercially 
available  lenses  have  been  applied  to  these  uses  under  conditions 
widely  different  from  those  for  which  such  lenses  were  originally 

As  suggested  above,  particular  considerations  may  justify  the 
design  of  special  lens  systems  in  which  improved  optical  efficiency 
may  be  attained  by  giving  close  attention  to  the  influence  of  the 
various  factors  that  determine  the  performance  of  the  instrument. 
In  some  cases,  sharp  definition  may  be  required  only  over  a  limited 
field  and  under  conditions  where  a  lens  of  low  relative  aperture  can  be 
employed.  In  case  a  photographic  material  of  low  speed  is  used, 
it  may  be  necessary  to  increase  the  relative  aperture  to  a  point  where 
the  definition  will  be  affected. 

At  the  Bell  Telephone  Laboratories  consideration  has  been  given 
to  the  choice  of  a  lens  system  that  is  required  to  work  with  a  low- 
speed  emulsion  under  illumination  conditions  that  necessitate  the 
use  of  the  high  relative  aperture  of //1. 5.  It  is  also  necessary  that 
this  lens  shall  give  the  best  possible  definition  over  a  limited  angular 
field  of  approximately  3.5  degrees.  The  object  consists  of  a  small 
illuminated  rectangular  aperture,  which  is  imaged  at  the  film  plane 
at  a  magnification  of  approximately  0.5.  The  particular  lens  that 
was  used  for  this  purpose  served  well  until  it  became  desirable  to 
increase  the  sharpness  of  the  image.  Lens  bench  examination  of  the 
image  structure  indicated  the  presence  of  axial  chromatic  aberration. 

A  photographic  method  of  measuring  axial  chromatic  aberration 
has  been  applied  to  a  study  of  this  and  similar  lenses.  The  method 
involves  the  projection  of  an  image  formed  by  the  lens  under  test  onto 
a  steeply  inclined  photographic  plate. 

Fig.  1  shows  schematically  the  apparatus  used.  The  slit  of  a 
constant  deviation  spectrometer  is  illuminated  by  a  small  coil  fila- 
ment tungsten  lamp  and  condenser.  These  units  are  adjusted  to 
form  an  out-of -focus  image  of  the  closely  spaced  coil  filament  at  the 
slit.  The  eyepiece  of  the  spectrometer  has  been  removed,  and  a  test 

April,  1933] 



object  consisting  of  five  transparent  lines  0.001  inch  wide  and  0.250 
inch  long,  separated  by  opaque  lines  of  the  same  dimensions,  is 
placed  at  the  approximate  focus  of  the  telescope  objective.  Im- 
mediately behind  this  test  object  is  located  a  small  piece  of  finely 
ground  glass,  which  serves  to  permit  filling  of  the  aperture  of  the 
lens  under  test,  which  is  shown  to  the  right  of  the  test  object.  The 
lens  under  test  forms  an  image  of  the  test  object  at  a  magnification 
of  0.5.  The  total  width  of  the  test  object  is  limited  to  0.010  inch, 
in  order  that  a  reasonably  pure  monochromatic  radiation  will  be 
transmitted  to  the  lens.  A  16-millimeter  Bausch  &  Lomb  apochro- 



i        LAMP 

FIG.    1.     Schematic  diagram  of  apparatus  for  measuring  axial  chromatic 


matic  microscope  objective  serves  to  relay  the  image  of  the  test 
object  formed  by  the  lens  under  test  to  a  steeply  inclined  photographic 
plate  at  a  magnification  of  10.0.  The  image  formed  by  the  micro- 
scope lens  lies,  of  course,  in  a  plane  perpendicular  to  the  optical  axis, 
and  the  inclined  photographic  plate  records  a  trace  of  the  focal 
region  surrounding  a  focal  point.  The  position  of  the  constant 
deviation  prism  in  the  spectrometer  can  be  altered,  and  a  reading  of 
the  wavelength  scale  indicates  the  wavelength  of  the  radiation 
incident  upon  the  test  object.  Assume  that  a  wavelength  of  4000  A 
is  illuminating  the  test  object,  the  lens  under  test  will  form  an  image 



[J.  S.  M.  P.  E. 

of  the  test  object  that  will  lie  at  some  distance  in  advance  of  the 
first  principal  focal  point  of  the  microscope  objective.  The  image 
formed  by  the  microscope  objective  will  lie  at  a  definite  distance 
to  the  rear  of  its  second  principal  focal  point.  If  an  axial  movement 
of  the  image  of  the  test  object  formed  by  the  lens  under  test  occurs, 
it  is  obvious  that  a  shift  of  the  image  formed  by  the  microscope 
objective  will  also  occur. 

A  series  of  exposures  is  made  on  a  single  plate.  These  exposures 
differ  only  in  respect  to  the  wavelength  of  the  light  incident  upon 
the  test  object.  If  the  color  curve  is  not  flat,  the  images  of  the  test 




a:  75 


2   25 
















|6500                    6000 

5500                    5000 




FIG.  2.  The  transmission  characteristics  of  the  dense  flint  prism  used  in 
spectrometer;  also  a  correcting  factor  applied  to  exposures  to  compensate  for 
the  loss. 

object  formed  by  the  lens  under  test  will  occupy  different  image 
planes.  This  shift  of  image  plane  with  wavelength  will  be  indicated 
on  the  inclined  photographic  plate  as  a  change  in  position  of  the 
point  of  sharpest  definition.  This  change  in  position  will,  of  course, 
be  a  function  of  the  wavelength  of  light  used,  and  is  directly  depen- 
dent upon  the  nature  of  the  axial  chromatism  of  the  lens  under  test. 
In  this  manner  we  can  trace  a  curve  connecting  the  series  of  points 
on  the  inclined  photograph,  which  will  represent  on  a  greatly  en- 
larged scale  the  values  of  axial  chromatic  aberration  of  the  lens  under 

April  1933] 



The  dense  flint  prism  used  in  the  spectrometer  exercises  a  high 
absorption  in  the  ultra-violet  region.  Fig.  2  shows  the  transmission 
characteristic  of  this  prism,  and  also  shows  a  correction  factor  that 
is  applied  to  exposures  in  order  to  compensate  for  this  loss. 

Fig.  3  has  been  made  in  the  above  described  manner,  and  shows  a 



4  4OO 

FIG.  3.  Plate  combining  series  of  exposures  showing 
shift  of  image  plane  with  wavelength;  the  dots  show 
roughly  the  points  of  sharpest  definition. 

change  in  the  point  of  sharpest  definition  as  a  function  of  wave- 
length. The  black  dots  serve  only  roughly  to  locate  the  various 
points  of  sharpest  definition. 

Fig.  4  shows  a  comparison  between  computed  values  of  axial 
chromatic  aberration  and  values  obtained  by  three  methods  of 
measurement.  A  curve  is  shown  that  represents  a  visual  examination 



[J.  S.  M.  P.  E. 

of  the  lens  in  which  a  ten-power  eyepiece  was  used  with  the  16-mm. 
apochromat  micro-objective  in  the  normal  way.  A  direct-reading 
micrometer  gauge  was  attached  to  the  microscope,  focal  settings 

0.3      12 












:  O.I      4 


0       0 















J6500                   6000  1                   5500^ 
C                                    D 

00  T              4500                      14000 
F                             G               H 


FIG.  4.     Comparison  between  computed  values  of  axial  chromatic  aberration 
and  values  obtained  by  three  methods  of  measurement. 

FIG.  5. 

A  focal  region  plate  made  on  a  process  type  of  emulsion; 
exposure  constant  for  all  wavelengths. 

were  made  on  the  image  of  the  test  target  visually,  and  the  differences 
were  noted.  A  curve  is  also  shown,  designated  "focus  plates," 
which  resulted  from  an  examination  of  an  extended  series  of  photo- 
graphs of  the  image  of  the  test  object  obtained  with  the  16-mm.  micro- 

April,  1933] 



scope  objective  when  the  photographic  plates  were  placed  normal 
to  the  optical  axis  of  the  objective.  The  microscope  and  plate  were 
moved  longitudinally  through  an  extended  range,  and  many  ex- 
posures made  at  definite  settings  for  each  selected  wavelength. 
This  process  was  repeated  at  all  desired  wavelengths;  a  visual 
examination  of  the  plates  indicated  the  location  of  the  plane  of 
sharpest  definition,  and  a  curve  was  readily  plotted  that  shows 
these  results  in  graphical  form.  The  fourth  curve  was  derived  from 
the  focal  region  plate  shown  in  Fig.  3.  An  average  curve  would 
result  in  a  departure  of  less  than  0.001  inch  between  the  computed 


FIG.  6. 

A  more  favorable  condition  attained   by  using  a  newly 
designed  lens. 

and  all  the  observed  values.    The  particular  lens  used  for  these  tests 
has  an  equivalent  focal  length  of  1.500  inch. 

The  photographic  emulsion  with  which  this  lens  is  used  is  sensitive 
only  to  the  blue  and  violet,  and  Fig.  5  shows  a  focal  region  plate 
made  on  a  process  type  of  emulsion  for  which  a  constant  exposure 
has  been  given  at  all  wavelengths.  It  is  obvious  that  the  greatest 
photographic  effect  occurs  at  4200,  4400,  and  4600  A,  with  a  lesser 
effect  at  the  other  wavelengths  shown.  This  figure  shows  clearly 
the  unfavorable  state  of  axial  chromatic  correction  that  exists  in  this 
lens  over  the  portion  of  the  spectrum  to  which  this  material  is  sensi- 



[J.  S.  M.  P.  E. 

Consideration  of  these  results  by  the  lens  designer  has  led  to  the 
design  of  a  new  lens  for  which  a  much  more  favorable  condition  is 
attained,  as  shown  by  Fig.  6.  Fig.  7  shows  this  correction  plotted  on 
the  same  scale  used  on  Fig.  4.  The  departure  from  a  flat  character- 
istic is  of  the  order  of  0.001  inch  at  4000  and  5000  A.  At  intermediate 
values  where  the  radiation  is  most  effective  in  building  up  density, 
we  note  that  the  curve  is  essentially  flat.  Fig.  8  represents  focal 
region  exposures  for  both  the  above-mentioned  lenses,  made  in  a 


2  £ 

o  ro  £»  o  a 

11     1 






|6500                   6000 

5500                    5000  [                 4500     |                 J4000 


FIG.  7.     The  correction  in  Fig.  6  plotted  on  the  same  scale  as  in  Fig.  4. 

FIG.  8.     Focal  region  exposures  for  the  two  lenses. 

similar  manner,  excepting  that  the  spectrometer  was  removed 
and  the  tungsten  light  source  focused  directly  on  the  test  object. 
A  difference  in  the  quality  of  definition  offered  by  these  two  lenses  is 
readily  shown.  Contrast  is  decidedly  improved  with  the  new  lens, 
and  other  tests  have  indicated  a  very  definite  improvement  in  sharp- 
ness of  the  image.  Fig.  9  shows  values  of  axial  chromatic  aberration 
for  the  16-mm.  apochromat  microscope  objective  as  determined 
visually  at  Bell  Telephone  Laboratories,  and  also  shows  the  corre- 

April,  1933] 



spending  values  derived  by  computation.  The  author  wishes  to 
acknowledge  the  courtesy  of  the  Bausch  &  Lomb  Optical  Company 
in  making  these  data  available.  These  values  were  obtained  in 
order  to  determine  the  possible  influence  of  the  characteristics  of  the 
microscope  objective  on  the  results  obtained  with  the  focal  region 
plate  method. 

It  is  obvious  that  the  apochromatic  type  of  objective  offers  a  very 
flat  color  characteristic  over  an  extended  wavelength  range.  Such 
lenses  can  be  manufactured  in  the  smaller  sizes  with  a  high  relative 
aperture,  and  can  be  corrected  for  the  desired  magnification.  The 
increasing  use  of  this  type  of  objective  might  be  expected  where 


2  O.I 








•  : 




-•»-•—  ^— 


—  T 



60001  5500  5000  I 

D  F 


|  4000 

FIG.  9.     Axial  chromatic  aberration  for  the  16-mm.  apochromat  microscope 
objective;   also  corresponding  values  derived  by  computation. 

critical  definition  is  required  over  a  narrow  field.  The  limit  in  the 
size,  focal  length,  and  aperture  that  can  be  obtained  with  the  apo- 
chromat construction  appears  to  be  established  by  the  availability 
of  suitable  material  for  its  construction. 

Consideration  is  being  given  to  the  possible  application  of  the 
above-described  method  of  test  to  the  measurement  of  spherical 
aberration  in  lenses.  The  use  of  a  single  rectangular  aperture  at  the 
test  object,  together  with  a  series  of  apertures  immediately  in  front 
of  the  lens  under  test,  may  serve  to  make  possible  the  accurate 
determination  of  crossing  distances  for  the  various  zones  of  the 

C.  H.  FETTER** 

Summary. — In  timing  races  by  the  usual  method  employing  a  manually  operated 
stop-watch,  errors  are  liable  to  arise  independently  of  the  accuracy  of  the  timepiece. 
In  order  to  eliminate  this  cause  of  error,  a  system  of  timing  races  has  been  devised 
employing  a  motion  picture  camera,  with  which  are  photographed  a  very  accurately 
adjusted  chronometer  at  both  the  beginning  and  the  end  of  the  race,  and  the  contestants 
themselves  at  the  finish  line.  This  system  has  been  applied  successfully  at  recent 
important  athletic  meets  held  in  the  U.  S.;  particularly  at  the  Xth  Olympiad  held 
at  Los  Angeles  in  1932. 

From  the  earliest  recorded  history  of  man  we  have  seen  evidence 
of  human  interest  in  all  sorts  of  athletic  sports.  Track  and  field 
events  were  popular  in  the  days  of  ancient  Greece  and  our  present 
Olympic  Games  originated  there  centuries  ago.  Not  only  has  man 
always  been  interested  in  the  purely  competitive  angle  of  racing 
events,  but  in  recent  years  he  has  become  more  and  more  interested 
in  the  performance  of  the  individual  with  respect  to  time,  in  addition 
to  his  performance  against  a  suitable  competitor.  On  this  basis  na- 
tional and  world  records  have  been  established  in  order  to  classify 
the  performance  of  the  individual  in  terms  of  an  invariable  quantity 
such  as  time,  where  a  contestant  may  compare  his  own  performance 
either  with  that  of  some  one  who  preceded  his  athletic  activities, 
possibly  by  years,  or  with  other  contestants  in  different  localities. 

In  dealing  with  this  so-called  invariable  quantity,  time,  the  ordinary 
method  employed  of  timing  a  race  has  been  by  means  of  a  stop- 
watch. Until  several  years  ago  stop-watches  giving  time  to  a  pre- 
cision of  one-fifth  second  were  used,  but  more  recently  tenth-second 
stop-watches  have  been  universally  employed.  In  track  work,  for 
example,  the  competitors  are  started  by  the  firing  of  a  gun.  The 
timers  are  usually  located  near  the  finish  line  of  the  race  in  order  to 
time  the  finish  properly.  The  timer  operates  a  stop-watch  at  the 
flash  of  the  gun  when  the  race  is  started,  and  operates  it  again  as  the 

*  Reprinted  from  the  Bell  Telephone  Quarterly,  XI  (Oct.,  1932),  No.  4,  p.  293  . 
**  Electrical  Research  Products,  Inc.,  New  York,  N.  Y. 


runner  crosses  the  finish  line.  This  procedure  inherently  contains 
the  possibility  of  three  errors:  (1)  it  is  practically  impossible  for  a 
human  being  to  operate  a  stop-watch  coincident  with  the  firing  of  the 
gun  because  of  the  human  reaction-time  involved;  (2)  it  is  ex- 
tremely difficult  for  a  timer  to  operate  his  stop-watch  at  the  finish  of 
the  race  coincident  with  the  man's  crossing  the  line,  and  while  this 
error  is  probably  less  than  the  starting  error  because  the  timer  has  an 
opportunity  to  anticipate  the  finish,  it  is  still  very  much  in  evidence ; 
(3)  the  watch  itself  by  virtue  of  being  built  for  a  precision  of  a  tenth 
of  a  second  would  register  the  nearest  tenth  when  the  timer  has 
operated  it.  In  addition,  there  is  likely  to  be  an  accumulative  error 
in  a  stop-watch  depending  upon  its  adjusted  rate  as  a  timepiece. 

In  addition  to  the  question  of  time  performance,  judging  a  race  is 
by  no  means  a  simple  problem.  In  a  close  finish  it  may  be  very 
difficult  to  decide  not  only  who  is  first,  but  also  the  order  of  finish  of, 
for  example,  the  first  five.  A  runner  may  be  blanketed  by  a  competi- 
tor so  that  the  judge  is  confused  as  to  which  runner  he  is  called  upon  to 
judge.  As  a  matter  of  fact,  in  an  important  meet  not  long  ago  a  man 
who  ran  second  was  not  placed  at  all  because  of  the  human  error  in 

This  state  of  affairs  in  regard  to  track  events  has  been  known 
to  exist  for  some  years.  Four  or  five  years  ago  Mr.  Gustavus  T. 
Kirby,  Chairman  of  the  Advisory  Committee  of  the  Intercollegiate 
Association  of  Amateur  Athletes  of  America  (I.  C.  A.  A.  A.  A.),  who 
has  been  interested  in  amateur  sport  activities  for  many  years,  con- 
ceived the  idea  of  photographing  the  finish  of  a  race  in  order  to  de- 
termine the  proper  position  of  the  contestants.  He  included  in  this  the 
idea  of  somehow  photographing  the  time  of  the  contestants  as  well, 
and  in  1931  he  used  a  motion  picture  camera  that  photographed  both 
the  finish  of  the  race  and  the  face  of  an  ordinary  stop-watch.  The 
scheme  that  he  used  was  that  of  starting  the  stop-watch  before  the 
race  was  started,  and  recording  on  the  motion  picture  film  a  flash  of 
light  operated  by  a  contact  in  the  starter's  gun.  By  subtracting  the 
readings  on  the  photograph  of  the  stop-watch  at  the  beginning  from 
those  of  the  finish  of  a  race  the  time  could  be  determined  to  the 
nearest  tenth  of  a  second. 

In  the  summer  of  1931,  several  individuals  at  Electrical  Research 
Products,  Inc.,  were  discussing  the  possibilities  of  applying  to  the 
problem  in  some  way  Bell  System  technical  knowledge  of  precision 
timing  work.  This  was  done  in  complete  ignorance  of  any  progress 

334  C.  H.  FETTER  [j.  s.  M.  p.  E. 

that  had  been  made  along  this  line  and,  strangely  enough,  the  same 
conclusion  was  reached  that  was  found  by  Mr.  Kirby  and  his  asso- 
ciates; namely,  that  the  only  satisfactory  method  by  which  a  race 
could  be  timed  and  judged  was  to  use  a  high-speed  motion  picture 
camera  arranged  to  photograph  both  the  performance  and  the  time. 
Obviously,  this  process  would  provide  a  permanent  record  of  each 
event,  which  would  be  of  value. 

Through  a  fortunate  occurrence  in  endeavoring  to  investigate 
the  situation  those  engaged  in  the  work  met  Mr.  Kirby  and  discussed 
the  problem  with  him.  They  were  extremely  interested  to  learn  of 
his  activity  along  this  line,  and  felt  that  the  company  could  make  a 
very  important  contribution  to  the  improvement  of  timing  apparatus, 
in  that  it  could  build  a  frequency  standard  that  would  permit  timing 
if  necessary  to  one  one-hundredth  or  even  to  one  one -thousandth  of  a 
second.  The  need  of  such  precision  in  timing  a  foot-race  becomes 
evident  when  it  is  realized  that  in  the  faster  races,  including  races  as 
long  as  a  half  mile  or  a  mile,  a  man  may  run  a  yard  at  the  finish  in  a 
tenth  of  a  second.  After  discussing  this  matter  with  Mr.  Kirby,  work 
was  begun  to  develop  suitable  apparatus  for  experimental  use  at  the 
I.  C.  A.  A.  A.  A.  and  the  Olympic  Games  in  1932,  for  which  per- 
mission had  already  been  granted. 

Before  design  of  the  apparatus  was  begun,  at  least  on  a  model 
basis,  several  preliminary  requirements  as  to  its  operation  were 
established:  (1)  it  was  decided  that  for  this  use  a  precision  of  0.01 
second  would  be  satisfactory,  as  such  timing  is  accurate  to  within 
three  or  four  inches  in  the  position  of  the  runner;  (2)  use  of  the 
photographic  method  appeared  absolutely  essential;  (3)  it  was 
considered  desirable  to  devise  a  means  of  photographing  the  reading 
of  the  clock  at  the  finish  of  the  race  to  show  the  actual  time  of  the 
runner.  This  meant  that  the  clock  must  be  reset  to  zero  before 
the  start  of  the  race  and  be  started  practically  instantaneously  with 
the  firing  of  the  gun.  The  Bell  Telephone  Laboratories  were  asked  to 
design  a  tuning-fork  generator  and  a  motor-driven  clock  mechanism 
that  would  meet  these  requirements. 

In  the  development  of  this  system  it  was  decided  to  make  two 
clocks,  one  associated  with  the  camera,  with  which  the  time  and  the 
finish  of  the  runner  could  be  photographed  adjacently  on  the  same 
film;  and  another,  that  could  be  started  in  the  same  manner  as  the 
first  so  arranged  as  to  be  hand-stopped,  so  that  one  of  the  timers 
could  use  this  precision  clock  as  a  sort  of  "glorified"  stop-watch,  by 

April,  1933] 



means  of  which  the  time,  except  for  human  error  at  the  finish,  could 
be  read  to  the  hundredth  of  a  second  immediately  following  the  race. 
The  system  that  was  developed  consists  primarily  of  a  200-cycle 
tuning-fork  generator  which  drives  a  synchronous  motor  at  a  speed 
of  ten  revolutions  per  second.  The  motor  shaft  is  connected  to  a  clock 
mechanism  by  means  of  a  magnetic  clutch  so  arranged  that  the  clock 

FIG.  1.     The  200-cycle  generator. 

dials,  which  are  normally  reset  to  zero  and  are  stationary,  are  set  in 
motion  when  the  starter's  pistol  is  fired. 

In  designing  the  clock-work  itself,  some  consideration  was  given  to 
the  type  of  record  to  be  obtained.  First  of  all,  it  was  decided  to  use 
a  standard  16-mm.  camera,  which  takes  128  pictures  per  second. 
Inasmuch  as  most  of  the  picture  area  in  the  16-mm.  film  must  be 
devoted  to  the  action  of  the  contestants,  it  was  decided  to  use  three 



[J.  S.  M.  P.  E. 

rotating  dials  and  a  fixed  hair-line  in  order  to  obtain  the  time  on  the 
film  in  the  largest  possible  characters.  By  the  use  of  rotating  dials 
it  was  necessary  to  photograph  only  a  small  segment  of  the  entire 
dial  arrangement.  Three  concentric  dials  were  used.  The  inner 
dial  rotates  at  one  revolution  per  second  and  has  one  hundred  di- 
visions on  it.  The  middle  dial  rotates  at  one  revolution  per  minute 
with  sixty  divisions,  and  the  outer  dial  rotates  at  one  revolution 

FIG.  2.     Assembly  of  the  camera,  clock,  and  control  box. 

per  hour  with  sixty  divisions.     Thus  minutes,   seconds,   and  one- 
hundredth  seconds  can  be  conveniently  read. 

Fig.  1  shows  a  photograph  of  the  200-cycle  generator  used  in  this 
model  and  Fig.  2  shows  an  assembly  view  of  the  camera,  the  clock, 
and  a  control  box  designed  to  provide  the  necessary  power.  The 
whole  system  is  operated  from  alternating  current  of  110  volts. 

April,  1933] 



338  C.  H.  FETTER  [j.  s.  M.  P.  E. 

The  optical  system  provided  to  photograph  the  clock  dials  can  be 
seen  at  the  left  rear  end  of  the  main  camera  lens  assembly. 

This  system  was  first  tried  out  at  the  Columbia-Syracuse  track 
meet  at  Baker  Field,  New  York,  on  May  14,  1932.  Fig.  3  shows  the 
first  race  to  have  been  timed  with  this  system.  It  was  the  100-yard 
dash,  in  which  the  time  as  shown  to  the  nearest  hundredth  of  a  second 
was  10.26  seconds.  At  the  Princeton-Cornell  meet  at  Princeton  on 
May  21,  1932,  the  system  was  successfully  demonstrated,  and  on 
June  19,  1932,  the  apparatus  was  sent  on  the  Intercollegiate  special 
train  which  ran  from  New  York  to  Berkeley,  California,  for  demon- 
stration at  the  I.  C.  A.  A.  A.  A.  meet  there  on  July  1  and  2. 

An  example  of  the  results  obtained  at  Berkeley  is  illustrated  in 
Fig.  4,  which  shows  Carr  of  Pennsylvania  winning  the  440-yard  dash 
in  46.99  seconds.  Even  though  the  camera  operates  at  such  high 
speed,  all  the  final  events  on  Saturday,  July  2,  were  recorded  on  less 
than  60  feet  of  film,  because  the  camera  is  operated  only  as  the  runners 
cross  the  finish  line. 

At  Palo  Alto  on  July  15  and  16,  the  American  Olympic  try  outs 
were  held,  and  photographs  were  obtained  of  the  finish  of  every 
"heat"  and  "final"  at  those  tryouts.  As  an  example  of  how  difficult 
it  is  to  judge  a  race,  Fig.  5  shows  the  finish  of  the  100-meter  final  at 
these  tryouts.  Metcalf  finished  first  in  a  time  of  10.62  seconds,  but 
there  were  at  least  four  runners  who  were  not  more  than  a  yard  or  so 
behind  him.  Such  a  grouping  of  runners  shows  how  difficult  it  is  to 
judge  a  close  race  by  the  eye  alone.  Note  that  the  camera  position 
is  above  the  finish  line  as  well  as  in  line  with  it  so  that  it  becomes  less 
difficult  to  judge  the  finish  properly.  At  Palo  Alto  on  July  16,  the 
film  was  shown  to  the  American  Olympic  Committee,  and  great 
interest  in  the  timing  system  used  was  expressed.  As  a  matter  of 
fact,  the  committee  confirmed  one  of  its  own  decisions  through  the 
showing  of  the  pictures,  and  reversed  the  fourth  and  fifth  positions 
in  one  event  because  of  the  camera  evidence. 

From  July  31  to  August  7,  inclusive,  this  apparatus  was  in  use 
at  the  Xth  Olympiad  held  at  the  Olympic  Stadium  in  Los  Angeles, 
California.  A  few  days  prior  to  the  opening  of  the  games  some  of 
the  pictures  taken  at  Palo  Alto  were  shown  to  the  Olympic  Com- 
mittee, and  based  upon  that  evidence  the  following  status  was  given 
the  timing  system:  (1)  it  would  be  used  officially  for  judging;  (2) 
the  hand-stopped  clock  associated  with  the  system  would  be  used  as 

April,  1933  ]  NEW  WAY  OF  SPLITTING  SECONDS  339 

one  of  the  timers,  of  which  there  were  five;  (3)  it  would  be  used 
officially  for  timing  the  decathlon. 

The  camera  clock  was  located  60  feet  back  from  the  finish  line  and 
on  top  of  a  25-foot  steel  tower,  as  shown  in  Fig.  6.  Throughout  the 
Olympics  every  trial,  semi-final,  and  final  was  timed.  Fig.  7  shows 
Tolan  breaking  the  world's  record  in  the  200-meter  run  with  a 
camera-recorded  time  of  21.12  seconds.  His  official  time  for  this  race 
was  21.2  seconds.  Fig.  8  is  interesting  because  it  shows  one  of  the 
official  photographs  taken  from  the  top  of  the  judges'  stand  for  this 
same  race.  In  the  lower  left-hand  corner  can  be  seen  the  hand- 
stopped  clock;  and  the  timer,  who  is  operating  it,  is  kneeling  in  the 
immediate  foreground.  Fig.  9  shows  Lord  Burleigh  of  England  in 
fifth  place  of  the  110-meter  hurdles.  This  illustrates  how  the  time 
of  each  contestant  can  be  determined,  as  well  as  that  of  the  winner. 
This  picture  is  also  particularly  interesting  because  it  was  in  this  race 
that  Finlay  of  Great  Britain  was  awarded  third  place,  reversing  the 
decision  of  the  judges,  who  had  awarded  it  to  Keller  of  the  United 
States  before  the  pictures  were  seen.  The  foot  of  the  winner  is  just 
visible  at  the  left  side  of  the  picture  and  Finlay  is  running  in  lane  3. 
Keller  of  the  United  States  is  running  in  lane  7,  the  farthest  one  from 
the  camera.  Two  other  decisions  of  a  minor  nature  were  reversed 
by  the  judges  after  seeing  the  pictures. 

As  an  example  of  how  the  official  times  compared  with  the  recorded 
photographed  time,  figures  are  given  below  for  some  of  the  Olympic 
finals : 

Difference — Official 

Official  Camera  Time  Used  as 

Race                             Time  Time  Reference 

100-Meter  Run                            10.3  10.38  +.08 

110-Meter  Hurdle                        14.6  14.57  -.03 

200-Meter  Run                             21.2  21.12  -.08 

400-Meter  Run                             46.2  46.28  +.08 

400-Meter  Hurdle                        51.8  51.67  -.13 

800-Meter  Run                         1:49.8  1:49.70  -.10 

At  a  meeting  of  the  International  Amateur  Athletic  Federation 
after  the  games  were  over,  this  body  in  an  official  report  praised  the 
use  of  the  timing  system  and  recommended  that  hundredth-second 
timing  be  adopted  as  a  world  standard.  It  also  officially  invited  us 
to  time  the  Olympic  Games  to  be  held  in  Berlin  in  1936. 

While  at  the  Olympic  Games  in  California,  Mrs.  Amelia  Earhart 



[J.  S.  M.  P.  E. 

FIG.    7.      The  finish   of   the 

200-meter  race  at  the   Xth 


Xth  Olympiad  Committee,  Official  Photograph 

FIG.  8.     An  official  photograph  taken  from  the  judges'  stand 

April,  1933] 



Putnam,  having  seen  and  heard  of  this  method  of  timing,  stated 
that  it  should  certainly  be  used  for  airplane  races.  As  a  result  of  this 
statement,  the  National  Aeronautic  Association  was  approached; 
and  through  the  courtesy  of  Dr.  Lewis  and  other  members  of  the 
Contest  Committee,  the  apparatus  was  used  in  collaboration  with  the 

RACE  2 

<- Start  30:  1410 
Finish  30:  37.30-* 
Time  23.20  sec. 

Speed  289.32  MPH 
RACE  3 

Start  33:  25.78  -» 
^-Finish  33:  48.09 
Time  22.31  sec. 

Speed  300.86  MPH 
RACE  4 

«-  Start  35:  42.10 
Finish  36:  05.35-* 
Time     23,25     sec.  j 
Speed  288.70  MPH 


Start  39:  58.42-* 
4-Finish  40:  20.74 
Time  22.32  sec. 
Speed  300.  73  MPH  J 

FIG.  10.     Cleveland  air  races.     3-kilometer  speed  record.     Major  James 
Doolittle.     Average  speed  (four  consecutive  trials)  294.90  mi.  per  hr. 

official  timing  means  at  the  Cleveland  Air  Races,  August  28  to  Sep- 
tember 5,  inclusive.  In  order  to  time  a  straightaway  airplane  speed 
trial,  it  was  necessary  of  course  to  have  two  camera  clocks  operating 
in  synchronism  from  one  generator,  one  to  photograph  the  be- 

342  C.  H.  FETTER 

ginning,  a  second  to  photograph  the  finish  of  the  race.  The  second 
camera  was  obtained  and  modified,  and  two  camera-operated  clocks 
were  used  at  Cleveland.  All  the  straight-away  races  in  which  there 
was  any  indication  that  a  speed  record  might  be  broken  were  photo- 

Fig.  10  shows  Major  Doolittle  breaking  the  world's  record  for  land 
planes  over  a  3-kilometer  course.  These  pictures  are  not,  of  course, 
official;  but  it  is  interesting  to  note  that  the  official  average  speed 
made  by  Major  Doolittle  as  determined  by  the  official  method  was 
294.48  miles  per  hour,  while  the  speed  determined  by  the  camera 
clock  was  294.90  miles  per  hour. 







Summary. — Holding  temperature,  developing  time,  and  agitation  constant,  the 
following  relations  exist:  (1)  In  an  elon-borax-sulfite  developer,  sulfite  held  constant 
and  borax  varied  with  the  elon,  j  =  K  log  E  -\-  C,  where  E  =  elon  cone,  and  K  and 
C  =  constants:  (2)  In  an  elon-hydroquinone-borax-sulfite  developer,  hydroquinone 
and  sulfite  held  constant  and  borax  varied  with  the  elon,  7  =  K  log  E  +  C,  where 
E  =  elon  cone,  and  K  and  C  =  constants:  (3)  In  an  elon-hydroquinone-borax- 
sulfite  developer,  elon,  borax,  and  sulfite  held  constant,  7  =  K  log  H  +  C,  where 
H  =  hydroquinone  cone,  and  K  and  C  =  constants:  (4)  In  an  elon-hydroquinone- 
borax-sulfite  developer,  sulfite  held  constant  and  borax  varied  with  the  elon,  7  = 
Ki  log  E  +  Kz(log  E)(log  H)  +  K3  log  H  +  KI,  where  E  =  elon  cone.,  H 
=  hydroquinone  cone.,  and  K\,  K^,  K%,  K±  =  constants:  (5)  In  an  elon-hydro- 
quinone-borax-sulfite  developer,  7  and  sulfite  held  constant,  and  borax  varied  with 
the  elon,  there  exist  optimum  concentrations  of  elon  and  hydroquinone  for  maximum 

Carlton  and  Crab  tree1  have  stated,  "If  borax  is  added  to  convert 
the  elon  into  the  elon  base,  the  rate  of  development  increases  with 
the  elon  concentration.  The  gamma  produced  for  a  constant  time 
of  development  increases  as  a  linear  function  of  the  logarithm  of  the 
elon  concentration." 

The  purposes  of  this  investigation  were  as  follows : 

(1)  To  verify  the  statement  of  Carlton  and  Crabtree  concerning  the  exponential 
relation  between  elon  and  gamma  in  an  elon-borax-sulfite  developer. 

(2)  To  determine  whether  or  not  the  same,  or  any  other  relation,  exists  between 
elon  and  gamma  in  an  elon-hydroquinone-borax-sulfite  developer  (hydroquinone 
maintained  constant). 

(3)  To  determine  the  relation  between  hydroquinone  and  gamma,  if  any,  in  an 
elon-hydroquinone-borax-sulfite  developer  (elon  maintained  constant). 

*  Reprinted  from  /.  Franklin  Inst.,  214  (Aug.,  1932),  No.  2,  p.  223. 
**  Chemical  engineer,  Hollywood,  Calif. 


344  ALAN  M.  GUNDELFINGER  [J.  S.  M.  P.  E- 

(4)  To  determine,  if  possible,  the  relation  between  gamma,  elon,  and  hydro- 
quinone  in  an  elon-hydroquinone-borax-sulfite  developer  (elon  and  hydroquinone 
both  variable). 

(5)  To  derive  a  method  for  calculation  of  the  most  economical  concentrations 
of  elon  and  hydroquinone,  provided  that  the  function  of  gamma,  elon  and  hydro- 
quinone can  be  evaluated. 


(a)  Film  Stock. — In  performing  the  series  of  tests  for  this  investi- 
gation it  was  thought  advisable  to  use  negative  stock,  which  reacts 
considerably  better  with  borax  developers  and  has  greater  latitude 
than  positive  stock,  and  to  use  one  with  which  a  fair  amount  of  light 
could  be  used  in  the  dark  room.     Consequently,  Eastman  ortho- 
chromatic  No.  1201-171  was  chosen. 

(b)  Sensitometric  Exposures. — Sensitometric  strips  were  exposed 
on  an  Eastman  Type  lib  sensitometer  with  a  lamp  and  filter  ac- 
curately calibrated,  by  the  Eastman  Kodak  Co.,  as  to  intensity  and 
color  temperature  (5400 °K.)  and  a  time  scale  in  powers  of  \/2. 

(c)  Development. — Development  of  the  Sensitometric  strips  was 
performed  in  the  following  manner : 

Two  strips  were  fastened,  emulsion  side  up  and  adjacent  to  each 
other,  to  a  piece  of  plate  glass.  The  plate  of  glass  was  dropped, 
simultaneously  with  the  releasing  of  a  timing  device,  into  a  tray 
containing  just  sufficient  developer  to  cover  the  strips.  The  tem- 
perature of  the  developer  was  maintained  at  18°  =•=  1°C.  Immedi- 
ately after  dropping  the  plate  of  glass  into  the  developer,  brushing 
of  the  strips  was  started.  A  camel's-hair  brush,  wide  enough  to 
cover  both  strips,  was  used,  and  the  brushing  was  accomplished  with 
a  uniform  reciprocating  stroke  of  length  equal  to  that  of  the  strips. 
The  rate  of  brushing  was  maintained  as  constant  as  was  humanly 
possible.  At  the  instant  of  the  sounding  of  the  time  signal,  indicat- 
ing completion  of  the  required  development  time,  the  glass  plate  with 
its  attached  strips  was  transferred  bodily  to  an  adjacent  tray  con- 
taining hypo  solution,  after  which  the  strips  were  thoroughly  washed 
and  dried.  The  time  of  development  in  all  cases  was  maintained  at 
5.0  minutes,  and  the  time  of  hypo  immersion  was  considerably  more 
than  sufficient  for  the  complete  removal  of  all  undeveloped  silver 

(d)  Density   Determination. — Densities   on    the    developed    Sensi- 
tometric strips  were  determined  with  a  Western  Electric  densitom- 
eter  using  a  Bausch  &  Lomb  head  of  the  polarizing  type.     The 

April,  1933] 



observations  were  made  with  the  emulsion  side  of  the  strips  down- 
ward, against  the  diffusion  glass. 

(e)  Curve  Plotting. — In  plotting  the  H  &  D  curves,  the  average 
density  of  corresponding  exposures,  on  two  strips  developed  simul- 
taneously, was  plotted  against  the  logio  of  the  absolute  exposure. 

(/)  Developers. — All  developers  used  in  this  investigation  contained 
300.0  gm.  of  sodium  sulfite  per  gallon,  and  a  quantity  of  borax, 
per  gallon,  equal  to  the  weight  of  elon,  in  grams  per  gallon,  plus 
8.0.  In  explanation,  it  might  be  well  to  call  attention  to  the  fact 
that  since  elon  requires  approximately  an  equal  quantity,  by  weight, 
of  borax  in  order  to  be  converted  into  the  elon  base,1  this  arrange- 
ment was  utilized  so  that  a  theoretical  excess  of  8.0  gm.  of  free  borax 



*    0.8 


Curve  Mo 


O.44    O.S7    O69 
SO      SO       SO      SO 
2O       4.O      8O     /6O 
/O  O     /2.O     /6-O    24  O 
fya/J  3OO.O  3OOO  JOO-O  3OO.O 


-/.S3       -O.93       -O-35         0.27        0-&7 

FIG.  1.     H  &  D  curves  of  elon-borax-sulfite  developers. 

would  always  be  available  to  accommodate  the  slightly  low  pH 
value  of  hydroquinone  without  seriously  affecting  the  pH  value  of  the 

The  four  fundamental  developers  used  were  as  follows : 

Elon  (gm./gal.).. 
Borax  (gm./gal.) 
Sulfite  (gm./gal.) 

In  addition,  sixteen  more  developers  were  used  consisting  of  each 
of  the  above-tabulated  developers  containing,  in  addition,  2.0,  4.0, 
8.0,  and  16.0  gm.,  respectively,  of  hydroquinone  per  gallon. 



2  0 





10  0 











[J.  S.  M.  P.  E. 



Fig.  1  shows  the  H  &  D  curves  obtained  from  the  four  fundamental 
developers  without  hydroquinone.     Fig.  2  shows  the  curve  obtained 



FIG.   2. 



FIG.   3. 

Borax  Cone  --/#  Ogm  +gm.  E/dn)/oa/ 
5  u/  fife  Cone  --  300.0gm./ya/ 

Where  Kand  C=  Constants 
andE*E/on  Cone. 

E/on  Cone    (gm/ya/J 

0.2    030.405  1.0          2.0   304050  1 0.0        20.030.0 

Gamma    vs.    elon    concentration;     for    elon-borax-sulfite 

Curve  A/o.  / 

Ga/ns77a.  O.33 

fiey.  7/S770  //V//7/    *5~-O 

fc/TT./fO/J  2.O 


0.47    O.S<3    0.67 
S.O      S-O      &O 
4.O      SO     /6.0 
2.0      2.0      2.0 
/2.0    /6-O  24-0 

3OO.O3OO.O  3OO.O  3OO-O 


H  &   D   curves  for  elpn-hydroquinone-borax-sulfite  de- 
velopers (hydroquinone,  2  gms./gal.). 

by  plotting  gamma  against  log  elon  concentration.     Examination  of 
the  curve  reveals  the  fact  that  the  general  equation  is: 

T  =  #log£  +  C  (1) 

where  K  and  C  =  constants  and  E  =  elon  concentration. 

April,  1933] 



Evaluating  the  constants  of  the  equation  for  the  curve  best  repre- 
senting the  data,  the  following  equation  is  obtained: 

7   =  0.4321ogi0E  +  0.18 
If,  now,  in  equation  (1),  7  is  differentiated  with  respect  to  E,  then, 



or  the  derivative  or  slope  of  the  7-elon  curve  is  inversely  proportional 
to  the  elon  concentration  and  the  proportionality  constant  is  the 
slope  of  the  7-log  R  curve.  In  other  words,  the  rate  of  change  of  7 
with  respect  to  elon  concentration,  holding  temperature,  agitation, 
and  development  time  constant,  is  inversely  proportional  to  the 
elon  concentration. 







/         2         3         4 
O-42    O-S/    O-6O    O.67 

MyarDfutnone    •• 


Su/f/te  "    3OO-O 


FIG.  4.     Same  as  Fig.  3  (hydroquinone  4  gms./gal.). 



Figs.  3,  4,  5,  and  6  show  the  H  &  D  curves  obtained  from  the  four 
fundamental  developers  containing  2.0,  4.0,  8.0,  and  16.0  gm.  hydro- 
quinone, respectively.  Fig.  7  shows  the  curves  obtained  by  plotting 
gamma  against  log  E  in  the  presence  of  constant  concentrations  of 
hydroquinone.  It  can  be  observed  quite  readily  that  the  same 
general  relation  exists  between  7  and  elon  concentration,  in  the 
presence  of  a  fixed  concentration  of  hydroquinone,  as  exists  in  the 
absence  of  the  latter.  That  relation  may  be  represented  also  by 
equations  identical  to  (7)  and  (2). 



[J.  S.  M.  P.  E. 


Inasmuch  as  the  reaction  of  hydroquinone,  as  well  as  other  de- 
veloping agents,  on  the  silver  halide  grain  is  primarily  one  of  reduc- 






Curve  Afo- 


Dev.  T/snefM/r?) 



OSS    0.64   0.7/ 

4.O      8.0    /6-O 
8O      30      Q.O     Q.O 
/O-O    /2.O     /6O    24O 
3OO.O  3OO-O  300.O  30O-O 

•  a  i 

-0.93      -0.33         0.27        O.&7 

FIG.  5.     Same  as  Fig.  3  (hydroquinone  8  gms./gal.). 




2.O  4.O  G.O  /6O 
••  /6-O  /6-O  /6.O  /6.O 
••  /O-O  /2.O  /6-O  24  O 
"  30O.O  300.O  3OO-O  300.O 

-2.  S3 

-0.93      -O.33        0.27       O.Q7 

FIG.  6.     Same  as  Fig.  3  (hydroquinone  16  gms./gal.). 

tion,  the  mechanics  of  which  should  in  all  cases  be  similar  if  not  ex- 
actly the  same,  it  should  be  expected  that  the  relation  between 
gamma  and  hydroquinone  is  the  same  as  that  between  the  former 
and  elon. 

April,  1933] 



Fig.  8  shows  the  curves  obtained  by  plotting  gamma  against  log 
hydroquinone  concentration,  in  the  presence  of  constant  concentra- 
tions of  elon.  The  data  for  these  curves  were  obtained,  likewise, 
from  those  of  Figs.  3,  4,  5,  and  6.  As  was  to  be  expected,  it  can  be 

Where  Kand  C  =  Constants 
and  E  -  Elon  Cone 

02     03  0405 

1.0         20    504050         IOO       200500 

FIG.  7.     Curves  of  gamma  vs.  log  elon,  for  various  constant  con- 
centrations of  hydroquinone;   data  obtained  from  Figs.  3  to  6,  incl. 



/.  23.        4. 

O.O67    OO53  O.O45  OO29 
2.O         40       8.0       /6.0 

y=KLog  H  +  C 
Where  Kand 'C= Constants 

ftyefroqumone  Cone  (gm/ga/.) 


0.2     03  0.405 



10.0        20.0  300 

FIG.  8.  Curves  of  gamma  vs.  log  hydroquinone  concentration  for 
various  constant  concentrations  of  elon;  data  obtained  from  Figs. 
3  to  6,  incl. 

observed  quite  readily  that  the  same  general  relation  exists  between 
gamma  and  hydroquinone,  in  the  presence  of  a  constant  concentra- 
tion of  elon,  as  exists  between  gamma  and  elon,  in  the  presence  of  a 



[J.  S.  M.  P.  E. 

fixed  concentration  of  hydroquinone.    This  relation  may  be  repre- 
sented by: 

7  =  K  log  H  +  C  (5) 

dH  =  H  (4) 

where  K  and  C  =  constants  and  H  =  hydroquinone  concentration. 


In  parts  III  and  IV  it  has  been  shown  that,  holding  temperature, 





Where  C,  and  C2  -  Constants 
and  H 

ttydroyuinone  Cone  (f 

O.I  0.2    0.3  04  OS  I.O          2.0    3.0  4.0 SO          100        20030.0 

FIG.  9.     Variation  of  the  constant  K  with  hydroquinone  concen- 
tration;  elon-hydroquinone-borax-sulfite  developers. 

agitation,  development  time,  and  the  concentration  of  the  remaining 
constituents  constant, 

7   =   F(E)     and     7   =  /(#) 

and  F(E)  and  f(H}  have  been  evaluated. 
Then,  if 

7  =   F(E,H] 

it  becomes  highly  desirable  to  evaluate  F(E,H). 

Examination  of  Fig.  7  reveals  the  fact  that  K  of  equations  (1) 
and  (2)  varies  with  the  hydroquinone  concentration  such  that 

K  = 


and  equation  (2)  becomes  a  partial  differential  equation,  as 


April,  1933] 



Likewise,  it  may  be  observed  from  Fig.  8  that  K  of  equations  (3) 
and  (4)  is  a  function  of  E,  or 

K  = 

such  that  equation  (4)  becomes  a  partial  differential  equation,  as 


If,  then,  X  of  equations  (1)  and  (2)  is  plotted  against  log  H,  as 
shown  in  Fig.  9,  it  is  found  that  there  is  a  linear  relation  between  K 
and  log  H,  and  $(H)  can  be  evaluated.  Then : 

K  =  t(H)  =  C,  -  C2  log  H  (7) 


Where  Cy  and  C+  -  Consfanfs 
and  £  =  E/on  Cone. 


0.2    0.5040.5         1.0         2.0         10.0       20.050.0 

FIG.  10.     Variation  of  the  constant  K  with  elon  concentration; 
elon-hydroquinone-borax-sulfite  developers. 

Similarly,  K  of  equations  (3)  and  (4)  is  shown,  in  Fig.  10,  to  bear 
a  linear  relation  to  log  E  such  that 

K  =  0(E)  =  Cz  -  C*  log  E  (8) 

where  C\,  Cz,  €3,  and  C4  are  constants. 

Combining  equations  (5)  with  (7)  and  (6)  with  (£),  there  results 

.  Ci  -  C2  log  H 




-  C4  log  E 



352  ALAN  M.  GUNDELFINGER  [j.  s.  M.  P.  E. 

7   =  (C,  -  C2  log  H)  log  E  +  /(#)  (11) 

Differentiating  7  with  respect  to  H  in  (11), 

d7  =     a  log  £  ,  # 

d#  H       ^  dH 

Combining  equations  (10)  and  (12), 

_d£  =  C3  -  C<  log  E      C2  log  £       C3  +  Cs  log  E 
dH  H  H  H 

which  on  integration  gives 

f(H)  =  (C3  +  C5  log  E)  log  H  +  Ct 

=   C3  log  H  +  C5(log  E)  (log  H)  +  C6 

where  C&  =  constant  of  integration.     And  on  combining  equations 
(11)  and  (14)  there  results 

7   =    CilogE  +   Cr(log  E)  (log  H)   +  C3logH  +  C6  (75) 


7    =   Ki  logic  £   +  ^2(logio  E)  (log,0  ff)   +  ^3  log,0  H  +  ^4  (^) 

Equation  (75)  becomes,  then,  the  general  equation  for 

7  =  /(£,  H) 

and  evaluating  the  constants  from  the  experimental  data,  the  equa- 
tion for  the  set  of  conditions  in  this  series  of  tests  becomes 

7    =   0.4021og10£   -  0.114(log10E)(log10#) 

+  0.217  logic  H  +  0.174 

where  £  =  elon  concentration  in  gm.  per  gallon  and  H  =  hydro- 
quinone  concentration  in  gm.  per  gallon. 




An  analysis  of  equation  (15)  of  part  V  reveals  the  fact  that  an 
infinite  number  of  combinations  of  elon  and  hydroquinone  will  satisfy 
the  equation  for  any  definite  gamma.  The  question  then  arises  as 
to  the  optimum  concentration  for  the  two  developing  agents.  The 
natural  answer  to  that  question  is  that  combination  of  concentra- 
tions which  will  formulate  the  least  expensive  developer. 

At  present  there  is  a  marked  difference  in  the  prices  of  elon  and 
hydroquinone,  that  of  the  former  amounting  to  slightly  over  three 
times  that  of  the  latter.  The  natural  impulse  would  lead  to  the  con- 
clusion, then,  that  the  least  expensive  developer  would  include 
the  least  possible  amount  of  elon. 

April,  1933] 



Such,  however,  is  not  the  case,  for  a  glance  at  the  slopes  of  the 
curves  of  Figs.  7  and  8  will  reveal  the  fact  that  elon  is  much  the 
more  powerful  reducing  or  developing  agent.  Consequently,  while 
it  is  the  more  expensive  of  the  two  agents,  a  lesser  concentration  of  it 
is  required  to  produce  a  definite  degree  of  development  than  that  of 
hydroquinone.  On  the  other  hand,  it  is  possible  to  utilize  a  concen- 
tration of  elon  which  is  too  high  for  economy. 

In  order  to  illustrate  this  point,  let  the  assumption  be  made  that 
the  costs  of  elon  and  hydroquinone  are  $3.30  per  pound  and  $1.00 
per  pound,  respectively,  and  that  the  desired  gamma  is  0.5.  Then 




/.O     2  0 

4.O     5.O      6.O      7.O 

9.O    /OO 

FIG.  11.     Curves  showing  relation  between  total  cost  of  developing 
agents  and  concentration  of  elon,  for  constant  gamma. 

by  virtue  of  this  assumption  and  equation  (17),  a  curve  (Fig.  11) 
has  been  constructed  showing  the  relation  between  the  total  cost  of 
developing  agents  per  unit  volume  of  developer  and  the  concentration 
of  elon. 

It  is  apparent  that  the  curve  has  a  marked  minimum  point  and 
that  there  are  distinct  optimum  concentrations  of  both  developing 
agents  for  maximum  economy.  It  is  perfectly  possible  to  determine 
the  minimum  point  of  this  curve  analytically  by  making  use  of  the 
calculus,  but  for  all  practical  purposes  the  increased  accuracy  is  of 


no  value  and  does  not  warrant  the  procedure,  which  is  quite  laborious. 
From  the  curve,  it  is  seen  that  an  elon  concentration  of  3.3  grn. 
per  gallon  corresponds  to  the  least  cost  of  a  developer  which  complies 
with  the  previously  mentioned  assumptions  and  is  to  be  utilized 
under  the  precise  experimental  conditions  of  this  investigation.  The 
corresponding  hydroquinone  concentration  is  found  from  equation 
(17)  to  be  5.5  gm.  per  gallon. 


1  CARLTON,  H.  C.,  AND  CRABTREE,  J.  I.:  "Some  Properties  of  Fine  Grain 
Developers  for  Motion  Picture  Film,"  Trans.  Soc.  Mot.  Pici.  Eng.,  XIII  (1929), 
No.  38,  p.  406. 




A.  N.  GOLDSMITH,  570  Lexington  Ave.,  New  York,  N.  Y. 

J.  I.  CRABTREE,  Eastman  Kodak  Company,  Rochester.  N.  Y. 


E.  I.  SPONABLE,  Fox  Film  Corp.,  New  York.  N.  Y. 
W.  C.  KUNZMANN,  National  Carbon  Co.,  Cleveland,  Ohio. 

J.  H.  KURLANDER,  Westinghouse  Lamp  Co.,  Bloomfield,  N.  J. 

H.  T.  COWLING,  Rochester,  N.  Y. 

Board  of  Governors 

H.  T.  COWLING,    1430  Monroe  Ave.,  Rochester,  N.  Y. 

J.  I.  CRABTREE,  Research  Laboratories,  Eastman  Kodak  Co.,  Rochester,  N.  Y. 

P.  H.  EVANS,  Warner  Bros.  Pictures,  Inc.,  1277  E.  14th  St.,  Brooklyn,  N.  Y. 

R.  E.  FARNHAM,  General  Electric  Co.,  Nela  Park,  Cleveland,  Ohio. 

O.  M.  GLUNT,  Bell  Telephone  Laboratories,  Inc.,  New  York,  N.  Y. 

A.  N.  GOLDSMITH,  570  Lexington  Ave.,  New  York,  N.  Y. 

H.  GRIFFIN,  International  Projector  Corp.,  90  Gold  St.,  New  York,  N.  Y. 

W.  C.  HUBBARD,  General  Electric  Vapor  Lamp  Co.,  Hoboken,  N.  J. 

R.  F.  MITCHELL,  Bell  &  Howell  Co.,  1801  Larchmont  Ave.,  Chicago,  111. 

J.  H.  KURLANDER,  Westinghouse  Lamp  Co.,  Bloomfield,  N.  J. 

W.  C.  KUNZMANN,  National  Carbon  Co.,  Cleveland,  Ohio. 

E.  HUSE,  Eastman  Kodak  Co.,  6706  Santa  Monica  Ave.,  Hollywood,  Calif. 

E.  I.  SPONABLE.  Fox  Film  Corp..  850  Tenth  Ave..  New  York.  N.  Y. 






Arrangements  for  the  approaching  Spring,  1933,  Convention,  to  be  held  at  New 
York,  April  24  to  28,  with  headquarters  at  the  Hotel  Pennsylvania,  are  rapidly 
proceeding,  the  plans  including  a  number  of  outstanding  presentations  that  will 
make  it  worth  every  one's  while  to  be  present  at  the  meeting.  Standardization 
is  to  play  an  important  part  in  the  proceedings.  The  economy  trends  in  sound 
picture  production  and  exhibition  that  the  industry  is  now  showing  will  be  dis- 

The  semi-annual  banquet  of  the  Society  is  to  be  held  on  April  26,  at  the  Hotel 
Pennsylvania.  An  evening  of  pleasure  and  interest  is  promised,  and  all  are  urged 
to  make  every  effort  to  attend. 

Mr.  W.  C.  Kunzmann,  chairman  of  the  Convention  Committee,  is  being  ably 
assisted  in  his  efforts  to  make  the  Convention  an  outstanding  success  by  the 
Local  Arrangements  Committee  under  the  chairmanship  of  Mr.  H.  Griffin. 

All  technical  sessions  will  be  held  in  the  Salle  Moderne,  on  the  roof  of  the  Hotel 
Pennsylvania.  Registration  will  be  opened  at  9  A.M.,  Monday,  April  24.  The 
registration  fee  will  be  $3,  and  the  banquet  charge  $4.50. 

Plans  are  being  made  to  assist  out-of-town  visitors  to  the  Convention  to  pass 
an  interesting  time  while  in  New  York,  and  special  film  programs  and  trips  of 
interest  will  be  arranged.  Final  details  of  the  program,  including  hotel  rates 
and  other  pertinent  information,  will  be  mailed  to  the  members  of  the  Society  at  a 
later  date.  Members  and  friends  of  the  Society  are  urged  to  make  every  effort  to 
attend  the  Convention. 



Arrangements  are  being  made  to  hold  an  exhibit  of  newly  developed  motion 
picture  apparatus,  in  order  to  acquaint  the  members  of  the  Society  with  the  newly 
devised  tools  of  the  industry.  This  exhibit  will  not  be  of  the  same  nature  as  the 
usual  trade  exhibit.  There  will  be  no  booths,  although  each  exhibit  will  be  al- 
lotted definite  space,  and  all  exhibits  will  be  arranged  in  one  large  room.  The 
following  regulations  will  apply: 

1.  The  apparatus  to  be  exhibited  should  be  new  or  have  been  developed  or 
improved  within  the  past  12  months. 

2.  Each  exhibitor  will  be  permitted  to  display  a  card  giving  the  name  of  the 
manufacturing  concern,  and  each  piece  of  equipment  shall  be  labeled  with  a 
plain  label  free  from  the  name  of  the  manufacturer. 



3.  A  technical  expert  capable  of  explaining  the  features  of  the  apparatus  ex- 
hibited must  be  present  during  the  period  of  the  exhibition. 

4.  A  charge  for  the  exhibit  will  be  made  in  accordance  with  the  space  occupied, 
as  follows:  up  to  20  sq.  ft.,  $10.00;  20  to  30  sq.  ft.,  $15.00;  30  to  40  sq.  ft.,  $20.00; 
40  to  50  sq.  ft.,  $25.00. 

Please  direct  requests  for  space  to  the  General  Office  of  the  Society,  33  West 
42nd  St.,  New  York,  N.  Y.,  stating  the  number  and  nature  of  the  items  to  be 


NEW  YORK,  N.  Y. 

APRIL  24-28,  1933,  INCLUSIVE 


H.  GRIFFIN,  Chairman 



J.  E.  ROBIN  J.  H.  SPRAY  T.  E.  SHEA 



E.  R.  GEIB  S.  R.  RENWICK 



assisted  by 








P.  H.  EVANS  J.  H.  SPRAY 

W.  C.  HUBBARD,  Chairman 



H.  GRIFFIN,  Chairman 



Officers  and  Members  of  Projectionists  Local  No.  306, 1.A.T.S.E.,  New  York. 


H.  T.  COWLING,  Chairman 

W.  WHITMORE,  Chairman 


All  technical  sessions  and  film  exhibitions  will  be  held  in  the  Salle 
Moderne,  Roof  Garden,  Hotel  Pennsylvania,  where  also  will  be  lo- 
cated the  registration  headquarters.  A  meeting  room  will  be  pro- 
vided for  the  Board  of  Governors  and  the  technical  committees  in 
the  Roof  Garden,  off  the  entrance  to  the  Salle  Moderne. 


A  private  parlor  suite  on  the  17th  floor  of  the  Hotel  Pennsylvania, 
directly  beneath  the  Convention  Headquarters,  will  be  reserved  for 
the  use  of  the  ladies. 


The  S.M.P.E.  Semi-annual  Banquet  and  Dance  will  be  held  in 
the  Grand  Ball  Room  of  the  Hotel  Pennsylvania,  Wednesday 
evening,  April  26,  at  7:30  P.M.:  an  evening  of  dancing  and  enter- 
tainment— no  banquet  speeches. 

Banquet  tickets  should  be  obtained  at  the  registration  head- 
quarters; tables  reserved  for  8  or  10  persons. 

Excellent  accommodations  are  assured  by  the  Hotel  Pennsyl- 
vania, and  minimum  rates  are  guaranteed.  Room  reservation 
cards  should  be  returned  immediately  to  the  Hotel  Pennsylvania  in 
order  to  assure  satisfactory  reservations.  Those  who  will  motor  to 
New  York  will  be  granted  special  daily  and  weekly  car  storage  rates 
at  the  modern  fire-proof  garage  adjoining  the  hotel. 

The  hotel  management  has  arranged  for  golfing  privileges  for 
members  at  the  Lido  Country  Club,  Lido  Beach,  Long  Island;  the 
Salisbury  Country  Club,  Westbury,  Long  Island;  and  the  Queens 
Valley  Golf  Club,  Inc.,  Forest  Hills,  New  York. 

April,  1933]  SOCIETY  ANNOUNCEMENTS  359 


The  exhibit  will  be  held  in  the  Roof  Garden  of  the  hotel,  adjacent 
to  the  registration  headquarters.  Please  communicate  with  Mr.  S. 
Harris,  Editor-Manager,  at  the  General  Office  of  the  Society,  33 
West  42nd  Street,  New  York,  N.  Y.,  regarding  space  and  exhibit 



The  morning  will  be  devoted  to  organization  of  the  convention, 
registration  of  members,  and  meetings  of  committees.  An  informal 
luncheon  for  members,  guests,  and  friends  will  be  held  in  the  Roof 
Garden  of  the  Hotel  Pennsylvania  at  12:30  P.M.  Several  addresses 
will  be  delivered  by  prominent  speakers. 

Luncheon  tickets  should  be  obtained  at  the  registration  desk  and 
will  be  collected  at  the  tables.  Don't  fail  to  attend. 

2:30  P.M.       Salle  Moderne. 

Convention  called  to  order. 

Address  by  President  A.  N.  Goldsmith. 

Report  of  the  Secretary,  Mr.  J.  H.  Kurlander. 

Report  of  the  Treasurer,  Mr.  H.  T.  Cowling. 

Convention  Announcements,  Mr.  W.  C.  Kunzmann. 

Papers  Committee,  Mr.  O.  M.  Glunt,  Chairman. 

Technical  papers  program. 
8:00  P.M.       Salle  Moderne. 

Interesting  program  of  recent  talking  motion  pictures. 
(Admission  by  registration  card.) 


9:30  A.M.        Salle  Moderne. 

Technical  papers  program. 
2:30  P.M.        Salle  Moderne. 

Technical  papers  program. 
8:00  P.M.        Bell  Telephone  Laboratories. 

Lecture  and  demonstration  by  Dr.  H.  E.  Ives.  Tickets 
for  this  session  will  be  supplied  by  the  registrars. 
The  laboratories  are  located  at  463  West  Street,  New 
York,  N.  Y. 

360  SOCIETY  ANNOUNCEMENTS  [J.  s.  M.  P.  E. 


9:30  A.M.       Salle  Moderne. 

Technical  papers  program. 

1 :00  P.M.       This  afternoon  is  left  open  for  recreation. 

7:30  P.M.        Grand  Ball  Room,  Hotel  Pennsylvania. 

S.M.P.E.  Semi-annual  Banquet.     Dancing  and  enter- 
tainment.    No  banquet  speeches. 


9:30  A.M.       Salle  Moderne. 

Technical  papers  program. 
2:30  P.M.       Salle  Moderne. 

Technical  papers  program. 
8:00  P.M.       Salle  Moderne. 

Popular  talk  and  motion  picture  program.     (Admission 
by  registration  card.) 


9:30  A.M.       Salle  Moderne. 

Technical  papers  program. 
2:30  P.M.       Salle  Moderne. 

Technical  papers  program. 

Open  Forum  and  Convention  Adjournment. 

Papers  Committee  Convention  Committee 

O.  M.  GLUNT,  Chairman  W.  C.  KUNZMANN,  Chairman 


The  monthly  meeting  of  the  New  York  Section  was  held  on  March  8  in  the 
auditorium  of  RCA  Photophone,  Inc.,  at  New  York,  N.  Y.,  approximately  one 
hundred  and  twenty  members  and  guests  attending.  Mr.  M.  C.  Batsel,  director 
of  the  Photophone  and  Applications  Division  of  the  RCA  Victor  Co.,  described 
briefly  the  development  and  application  of  the  new  RCA  high-fidelity  recording 
and  reproducing  equipment. 

Following  his  address,  a  number  of  short  and  feature  pictures  were  reproduced, 
in  order  to  exemplify  the  improvements  achieved  by  the  new  system.  The  Walt 
Disney  release,  Santa  Claus  in  Toyland,  a  Mickey  Mouse  short,  and  a  Van  Beuren 
animated  cartoon,  recorded  with  high-fidelity  equipment,  were  reproduced. 
Following  these  short  reproductions,  an  RKO  feature  picture  entitled  Our  Betters, 
starring  Constance  Bennett,  and  recorded  on  the  RCA  type  PR-4  variable  width 
recorder  (described  in  the  March,  1933,  issue  of  the  JOURNAL)  equipped  with  a 
special  high-frequency  response  galvanometer,  was  projected  and  reproduced. 
The  galvanometers  used  for  recording,  devised  by  Mr.  C.  Dreher,  were  designed 
to  have  an  approximately  linear  response  at  frequencies  up  to  8000  cycles. 

April,  1933]  SOCIETY  ANNOUNCEMENTS  361 

A  general  discussion  of  the  equipment  and  the  reproduction,  from  the  standpoint 
of  recording  and  reproducing  sound,  followed  the  demonstration;  after  which  the 
recording  and  reproducing  equipment  installed  in  the  auditorium  were  opened  to 
inspection  by  the  members,  and  were  ably  described  by  members  of  the  RCA 
Photophone  organization. 

Unusual  interest  was  shown  by  the  audience  in  the  new  equipment  and  in  the 
technical  endeavors  being  made  to  improve  the  quality  of  recording  and  repro- 
ducing; and  that  this  interest  was  real  and  that  the  meeting  was  quite  successful 
were  attested  to  by  the  fact  that  nearly  the  entire  audience  remained  until  the 
adjournment,  which  occurred  unusually  late. 

D.  HYNDMAN,  Secretary-Treasurer 


The  second  meeting  of  the  season  was  held  in  the  theater  of  Paramount  Pro- 
ductions, Inc.,  approximately  one  hundred  and  twenty-five  members  and  guests 
attending.  This  meeting  emphasized  further  the  plans  of  the  present  Board  of 
Managers  to  depart  from  the  usual  style  of  meeting  dealing  primarily  with  motion 
pictures  as  a  means  of  entertainment.  Although  the  importance  of  the  motion 
picture  is  admittedly  greatest  in  the  entertainment  field,  other  fields,  including 
those  of  advertising,  history,  education,  etc.,  are  developing  so  rapidly  that  the 
professional  motion  picture  engineer  is  obliged  to  take  cognizance  of  their  require- 
ments and  technological  needs.  That  excursions  into  these  fields  are  deemed 
worth  while  is  attested  to  by  the  attendance  at  the  meeting  and  the  amount  of  in- 
terest displayed. 

Mr.  J.  Dubray  had  been  appointed  chairman  of  the  Program  Committee  for 
this  meeting,  and  had  ably  arranged  for  a  session  devoted  to  the  application  of 
motion  pictures  by  the  medical  profession.  A  business  appointment  unfortu- 
nately preventing  Mr.  Dubray  from  attending  the  meeting,  Dr.  D.  MacKenzie 
kindly  consented  at  the  request  of  Section  Chairman  E.  Huse  to  act  as  chairman 
of  the  meeting,  in  which  capacity  he  ably  kept  up  the  spirits  of  those  viewing 
the  pictures  who  were  unaccustomed  to  witnessing  six-inch  close-ups  of  human 

The  program  opened  with  the  projection  of  a  two-reel  picture  of  an  appendec- 
tomy, in  35-mm.  Technicolor,  followed  by  another  showing  the  removal  of  a 
breast  cancer;  both  operations  having  been  performed  by  Dr.  M.  Kahn,  of  the 
Cedars  of  Lebanon  Hospital.  These  pictures  were  of  particular  interest  in  that 
they  had  been  photographed  by  a  professional  cameraman,  Mr.  H.  Green,  under 
the  supervision  of  a  commercial  producing  company. 

There  were  also  projected  two  reels  of  a  picture  dealing  with  plastic  surgery,  the 
work  of  Dr.  H.  L.  Updegraf,  also  of  the  Cedars  of  Lebanon  Hospital,  in  35-mm. 
Magnacolor;  followed  by  a  16-mm.  film  depicting  the  complete  case  history  of  the 
reconstruction  of  a  burned  face.  The  skill  shown  in  this  work,  which  involved 
fourteen  operations  over  a  period  of  as  many  months,  evoked  a  genuine  response  of 
admiration  from  the  audience.  Dr.  Updegraf 's  exhibition  was  accompanied  by  an 
explanatory  talk  that  left  little  doubt  in  the  minds  of  the  spectators  as  to  the  value 
of  this  kind  of  application  of  motion  pictures. 

Two  reels  of  16-mm.  film  illustrating  the  technics  of  cystectasy  and  prostatec- 


tomy,  were  exhibited  by  Dr.  E.  Belt,  who  accompanied  the  projection  with  a  de- 
scription of  the  surgery  and  the  methods  employed  in  obtaining  the  pictures. 

Dr.  J.  C.  Irwin  screened  about  1000  feet  of  16-mm.  film  showing  three  examples 
of  Caesarian  section.  An  interesting  feature  of  this  showing  was  the  progress  that 
had  been  made  in  the  photography  of  the  three  successive  operations. 

Dr.  Lozier,  of  the  University  of  Southern  California,  closed  the  exhibit  with  a 
screening  of  dental  films,  demonstrating  the  advantages  of  superspeed  panchro- 
matic negative  film  over  the  orthochromatic  stock  used  some  years  ago. 

At  the  invitation  of  the  chairman,  the  members  of  the  section  were  addressed 
briefly  by  Mr.  W.  C.  Kunzmann,  vice-president  of  the  Society.  Mr.  Kunzmann 
voiced  the  appreciation  of  the  Board  of  Governors  and  the  officers  of  the  Society 
for  the  great  activity  being  shown  by  the  Pacific  Coast  Section. 

The  large  attendance  and  the  great  amount  of  interest  shown  in  the  subject  of 
the  meeting  were  very  gratifying,  indicating  that  fields  of  application  of  motion 
pictures  not  frequently  explored  hold  for  the  motion  picture  engineer  many  fea- 
tures of  technical  and  general  interest. 

G.  RACKETT,  Secretary-Treasurer 


Several  meetings  of  representatives  of  the  several  projection  committees  have 
recently  been  held  for  the  purpose  of  studying  the  various  problems  involved  in 
measuring,  and  in  arriving  at  recommendations  for,  the  brightness  of  projection 
screens  and  the  illumination  of  theater  auditoriums. 

Upon  invitation  of  the  S.M.P.E.,  a  committee  was  established  by  the  Illuminat- 
ing Engineering  Society,  under  the  chairmanship  of  Prof.  S.  R.  McCandless  of 
Yale  University,  for  the  purpose  of  collaborating  with  the  S.M.P.E.  group.  The 
latter  was  consequently  officially  organized,  under  the  name  given  above,  as  a  sub- 
committee of  the  Projection  Screens  Committee.  The  personnel  of  the  sub-com- 
mittee follows: 

S.  K.  WOLF,  Chairman 

A.  C.  HARDY  (Chairman,  Projection  Theory  Committee) 
W.  F.  LITTLE  (Member,  Projection  Screens  Committee) 
H.  RUBIN  (Chairman,  Projection  Practice  Committee) 
H.  B.  SANTEE  (Chairman,  Sound  Committee) 


At  a  meeting  held  on  March  15,  at  New  York,  N.  Y.,  a  draft  of  the  report  to  be 
presented  at  the  convention  in  April  was  read  to  the  Committee  by  Chairman 
Rubin,  for  discussion  and  revision.  The  report  describes  the  special  test  reels 
that  have  been  developed  by  the  Committee,  mentioned  in  previous  issues  of  the 
JOURNAL,  and  a  special  tool  that  has  been  devised  for  the  purpose  of  aligning  the 
arc  lamp  with  the  optical  axis  of  the  projector;  and  discusses  various  problems 
incident  to  change-over  marks  and  their  location,  and  positive  print  density  and 
studio  screen  illumination. 

April,  1933]  SOCIETY  ANNOUNCEMENTS  363 


Bausch  &  Lomb  Optical  Co. 
Bell  Telephone  Laboratories 
Burnett-Timken  Laboratories 

Eastman  Kodak  Co. 
Electrical  Research  Products,  Inc. 

National  Carbon  Co. 

RCA  Victor  Co.,  Inc. 




By  action  of  the  Board  of  Governors,  October  4,  1931 ,  this  Honor  Roll  was  estab- 
lished for  the  purpose  of  perpetuating  the  names  of  distinguished  pioneers  who  are 
now  deceased; 







It  may  have  been  fate  that  prompted 
the  perfecting  of  the  first  Eastman 
motion  picture  film  just  when 
Edison's  first  projector  demanded  it. 

But  it  was  time's  judgment  of  its 
merit  that  again  and  again  confirmed 
Eastman  film  as  a  leader  in  the  in- 
dustry it  helped  to  father. 

Today  it  is  Eastman  Super-sensitive 
Panchromatic  Negative  that  points 
the  way  to  new  heights  of  accom- 
plishment, in  a  new  era  of  cinematog- 
raphy. Eastman  Kodak  Company 
(J.  E.  Brulatour,  Inc.,  Distributors). 





Volume  XX  MAY,  1933  Number  5 



An  Introduction  to  the  Experimental  Study  of  Visual  Fatigue. 

P.  A.  SNELL  367 

Avoidance  of  Eye  Fatigue F.  H.  RICHARDSON  391 

RCA  Victor  High  Fidelity  Film  Recording  Equipment 

S.  READ,  JR.  396 

A  New  Process  of  Television  Out  of  Doors 


Book  Reviews 444 

Officers 446 

Committees 447 

Society  Announcements 450 





Board  of  Editors 

J.  I.  CRABTREE,  Chairman 


O.  M.  GLUNT  F.  F.  REN  WICK 

Published  monthly  at  Easton,  Pa.,  by  the  Society  of  Motion  Picture  Engineers. 

Publication  Office,  20th  &  Northampton  Sts.,  Easton,  Pa. 
General  and  Editorial  Office,  33  West  42nd  St.,  New  York,  N.  Y. 

Copyrighted,  1933,  by  the  Society  of  Motion  Picture  Engineers,  Inc. 

Subscription  to  non-members,  $12.00  per  annum;  to  members,  $9.00  per  annum, 
included  in  their  annual  membership  dues;  single  copies,  $1.50.  A  discount 
on  subscriptions  or  single  copies  of  15  per  cent  is  allowed  to  accredited  agencies. 
Order  from  the  Society  of  Motion  Picture  Engineers,  Inc.,  20th  and  Northampton 
Sts.,  Easton,  Pa.,  or  33  W.  42nd  St.,  New  York,  N.  Y. 

Papers  appearing  in  this  Journal  may  be  reprinted,  abstracted,  or  abridged 
provided  credit  is  given  to  the  Journal  of  the  Society  of  Motion  Picture  Engineers 
and  to  the  author,  or  authors,  of  the  papers  in  question.  The  Society  is  not  re- 
sponsible for  statements  made  by  authors. 

Entered  as  second  class  matter  January  15,  1930,  at  the  Post  Office  at  Easton, 
Pa.,  under  the  Act  of  March  3,  1879. 



Summary. — Previous  work  has  shown  that  fatigue  of  the  visual  process  as  a  whole 
is  not  directly  measurable;  it  is  therefore  necessary  to  adopt  the  alternative  method  of 
studying  the  individual  processes  involved  in  vision.  An  analysis  of  the  studies 
so  far  made  on  these  unit  functions  shows  that  the  motor  processes  involved  are  not 
readily  fatigued;  ineffective  activity  of  these  processes,  however,  rapidly  leads  to  sensa- 
tions of  fatigue.  This  activity  results  from  inadequate  sensory  projection,  whether 
the  inadequacy  is  a  result  of  difficult  external  seeing  conditions  or  of  decreased  efficiency 
of  the  retinal  processes.  Experiments  were  performed  which  showed  that:  (1)  the 
effective  intensity  of  a  given  stimulus  was  affected  considerably  by  the  previous  activity 
of  the  retina;  (2)  contrasts,  and  especially  flicker ,  produced  a  marked  retinal  fatigue; 
(3}  the  site  of  this  fatigue  lay  in  the  retinal  structures  behind  the  sense  endings  rather 
than  in  the  sense  endings  themselves.  It  is  concluded  that  retinal  fatigue  contributes 
a  larger  factor  to  visual  fatigue  than  has  hitherto  been  supposed;  as  long  as  the  visual 
task  is  such  that  the  factors  producing  a  decrease  in  retinal  efficiency  are  minimal, 
as  is  not  usually  the  case  in  viewing  the  motion  picture,  visual  fatigue  will  not  super- 
vene with  unusual  rapidity. 

At  the  very  beginning  of  a  consideration  of  the  problem  of  visual 
fatigue,  it  is  apparent  that  no  solution  will  be  forthcoming  until 
after  a  prolonged  attack  by  many  investigators.  The  amount  of 
work  that  can  be  accomplished  in  one  year  is  small  compared  with 
what  is  yet  to  be  done.  Whatever  progress  can  be  made  in  this 
short  interval  of  time  is  valuable  only  in  proportion  to  the  amount 
of  solid  foundation  laid  for  the  benefit  of  those  who  will  continue 
toward  the  solution.  In  order  to  proceed  on  a  fundamental  basis, 
therefore,  this  study  was  begun  and  carried  out  along  three  related 
lines:  (1)  a  partial  compilation  of  the  studies  so  far  made  on  visual 
fatigue;  (2)  an  analysis  of  some  recent  advances  in  the  field  of  visual 
physiology  which  are  pertinent  to  this  study;  (3)  the  undertaking 
of  experimental  work  leading  to  the  establishment  of  new  facts 
aiding  in  the  further  elucidation  of  the  problem. 

It  is  obviously  desirable  to  agree  on  a  meaning  for  the  term  fatigue. 

*  Presented  at  the  Spring,  1933,  Meeting  at  New  York,  N.  Y. 
**  S.M.  P.  E.  Fellow  at  the  University  of  Rochester,  Rochester,  N.  Y. 


368  PETER  A.  SNELL  [j.  S.  M.  P.  E. 

To  the  layman  fatigue  implies  the  idea  of  physical  tiredness,  usually 
the  result  of  work,  and  includes  in  its  connotation  loss  of  efficiency 
and  lack  of  desire.  In  this  sense  the  term  is  too  broad  for  our  pur- 
pose. In  strictly  physiological  nomenclature,  fatigue  has  a  much 
more  definite  meaning.  This  meaning  is  expressed  in  the  following 
rather  technical  definition:  "Fatigue  is  a  metabolic  state  resulting 
from  the  inability  of  anabolic  processes  to  proceed  as  rapidly  as 
catabolic  ones  during  the  activity  of  an  organ  or  part."  This 
definition  puts  fatigue  definitely  with  the  phenomena  peculiar  to 
living  tissues,  draws  attention  to  fatigue  as  a  state  apart  from  any 
other  state  or  situation  of  such  tissues,  and  emphasizes  the  role  of 
activity  in  the  establishment  of  the  state.  The  definition  properly 
omits  reference  to  the  manifestations  of  fatigue,  as  they  are  rather 
characteristic  of  the  particular  organ  subject  to  fatigue  than  of  the 
state  itself. 

We  can  not  consider  fatigue  without  reference  to  the  phenomenon 
of  adaptation.  The  above  definition  of  fatigue  is  also  a  definition 
of  adaptation.  One  can  consider  that  in  the  case  of  adaptation  the 
catabolic  reaction  is  desirable;  in  the  case  of  fatigue,  it  is  undesir- 
able. It  seems  that  nature  has  made  the  best  of  the  situation,  and 
upon  occasions  has  turned  the  occurrence  of  the  fatigue  reaction  to 
a  useful  purpose.  Adrian1  distinguishes  somewhat  more  definitely 
between  the  two  in  describing  fatigue  as  a  "decline  in  activity  caused 
by  the  previous  activity  of  the  organ,"  and  adaptation  as  a  "decline 
in  excitability  caused  by  the  stimulus — the  change  in  the  environ- 
ment— quite  apart  from  the  existence  of  activity."  This  definite 
distinction  is  not  applicable  to  any  situation,  however,  since  in 
general  the  state  of  any  organ  at  a  given  time  is  inseparably  linked 
up  both  with  its  previous  activity  and  with  the  stimulus  existing  at 
that  time. 

Actually,  there  are  characteristic  differences  between  fatigue  and 
adaptation.  (Hereafter  in  this  discussion  fatigue  refers  to  physio- 
logical fatigue.)  Adaptation  is  a  reaction  which  occurs  immediately 
following  the  presentation  of  the  situation  calling  for  it,  takes  place 
rapidly,  brings  about  a  benefit  to  the  organism,  and,  finally,  has  a 
slight,  if  any,  subjective  effect  upon  the  organism.  Fatigue,  on  the 
other  hand,  is  delayed  in  its  occurrence  following  the  presentation 
of  an  adequate  stimulus,  is  slow  to  develop,  brings  about  harm  to  the 
animal  economy,  and,  finally,  has  a  rather  profound  effect  upon  the 
organism.  Yet,  in  spite  of  these  differential  characteristics,  fatigue 

May,  1933  ]       EXPERIMENTAL  STUDY  OF  VISUAL  FATIGUE  369 

and  adaptation  can  not  be  definitely  and  quantitatively  differentiated 
in  any  given  set  of  conditions. 

Ophthalmologists  as  a  group  are  outstanding  in  contributions  to 
the  study  of  the  problem  of  visual  fatigue,  since  they  are  in  a  position 
to  recognize  its  importance  as  well  as  to  observe  the  sequence  of 
cause  and  effect  in  its  occurrence.  In  his  practice  the  ophthalmolo- 
gist sees  cases  representative  of  the  whole  range  of  fatigue  states, 
from  the  simplest  so-called  "eye-strain"  to  the  severe  crippling 
condition  of  asthenopia.  If  we  examine  this  whole  range  of  condi- 
tions, we  find  that  the  differences  between  them  are  almost  entirely 
those  of  degree.  Asthenopia,  according  to  Jackson,2  refers  to  the 
condition  present  in  "those  unable  to  use  the  eyes  for  more  than  a 
very  brief  time  without  pain,  although  the  eyes  are  without  recog- 
nizable ocular  conditions  to  account  for  this  disability."  The 
pain,  hyperemia,  lacrymation,  and  other  symptoms  and  signs  present 
in  this  condition,  are  the  same  in  nature  and  sequence  as  those 
present  in  cases  of  eye-strain  due  to  a  simple  refractive  error  or  any 
other  cause.  Lancaster's3  description  of  the  symptoms  and  signs 
occurring  as  a  result  of  ocular  work  under  faulty  illumination  is 
practically  the  same  as  Jackson's4  account  of  those  manifesting  the 
existence  of  visual  fatigue.  There  is  no  doubt  that  the  eye  always 
responds  by  the  same  fatigue  reaction  to  any  and  all  conditions  under 
which,  as  Lancaster  has  shown,  seeing  is  a  more  difficult  task  than 
the  visual  mechanism  is  prepared  to  handle. 

Anything  causing  difficult  seeing  will  result  in  eye-strain.  In  the 
production  of  visual  fatigue  under  conditions  for  seeing  which  are 
not  unfavorable,  it  is  the  decline  in  efficiency  of  the  eye  after  a 
fairly  prolonged  period  of  use  which  brings  about  the  condition  of 
difficult  seeing  resulting  finally  in  eye-strain.  If  the  eye  or  visual 
apparatus  is  exceptionally  poor,  average  conditions  for  seeing  are 
too  difficult  for  the  eye  to  handle  from  the  start,  and  eye-strain 
appears  after  a  very  short  exposure.  If  the  external  conditions  for 
seeing  are  unfavorable,  even  though  the  eye  is  normal  or  average  in 
ability,  eye-strain  will  result  after  a  fairly  short  interval.  Luckiesh 
and  Moss5  have  emphasized  this  relationship  between  the  external 
and  the  physiological  factors  in  ocular  function  by  the  consideration 
of  seeing  as  "a  partnership  of  lighting  and  vision." 

Eye-strain  which  has  progressed  far  enough  to  be  causing  sub- 
jective symptoms  has  become  truly  severe.  Jackson4  has  empha- 
sized the  fact  that  headache  and  eyeache  indicate  the  establishment 

370  PETER  A.  SNELL  [j.  S.  M.  P.  E. 

of  a  pathological  reaction  rather  than  temporary  weariness. 
"Normal  visual  fatigue  rarely  rises  into  consciousness.  Only  when 
the  organism  in  response  to  long  continued  or  repeated  excessive 
fatigue  has  developed  a  method  of  translating  this  into  discomfort 
or  pain  does  it  develop  into  symptoms  that  bring  patients  to  us  for 

Herein  lies  the  difficulty  in  finding  an  easy  approach  to  the 
study  of  this  problem.  We  can  not  tell  when  a  normal  state  of 
fatigue  has  been  produced,  because  we  are  not  immediately  conscious 
of  its  presence  nor  are  we  conscious  of  the  increasing  effort  necessary 
to  counterbalance  it.  Many  attempts  have  been, made  to  demon- 
strate the  occurrence  of  normal  visual  fatigue  by  following  the 
changes  in  time  necessary  to  perform  a  given  task  after  a  preliminary 
variable  fatiguing  period,  or  by  following  changes  in  external  condi- 
tions necessary  to  keep  the  eyes  working  at  a  given  pace.  Some  of 
these  experiments  are  extremely  interesting.  Luckiesh  and  Moss5 
cite  an  experiment  in  which  the  time  required  to  read  a  given  amount 
of  printed  matter  when  the  page  was  stationary  was  compared  with 
that  required  when  it  was  vibrating.  The  experiment  showed  that 
although  subjectively  the  task  was  quite  obviously  more  difficult 
when  the  page  was  vibrating,  nevertheless  the  time  consumed  was 
practically  the  same  in  both  cases.  Ives,6  in  another  experiment, 
found  that  there  was  little  change  in  visual  acuity  following  pro- 
longed visual  work  under  poor  as  compared  with  good  lighting  condi- 
tions. In  a  different  type  of  experiment,  involving  a  visual  task 
which  called  for  prolonged  use  of  the  extraocular  muscles,  Cobb 
showed  that  the  ability  of  the  subject  to  perform  the  task  did  not 
change  when  a  high  illumination  level  was  substituted  for  a  low  one, 
although  the  task  set  elicited  a  severe  visual  fatigue. 

Luckiesh  and  Moss5  have  suggested  that  the  failure  to  demonstrate 
visual  fatigue  by  these  methods  is  due  to  the  biological  principle  of 
compensation.  After  fatigue,  the  body  or  any  part  of  it  can  still 
perform  a  given  task  as  quickly  and  as  accurately  as  before;  because 
it  has  the  faculty  of  drawing  on  reserve  forces  only  when  reserves  are 
needed,  and  of  conserving  any  energy  remaining  so  that  it  will  be 
available  for  the  continuance  of  response  at  the  previous  level.  The 
occurrence  of  visual  fatigue  is  accompanied  by  greater  difficulty  in 
seeing,  not  by  less  ability  to  see. 

It  is  evident  that  the  demonstration  and  quantitative  measure- 
ment of  visual  fatigue  offers  an  unusually  complicated  problem. 

May,  1933]          EXPERIMENTAL  STUDY  OF  VISUAL  FATIGUE  371 

It  is  possible  to  recognize  the  presence  of  visual  fatigue,  and  to  state 
with  some  degree  of  certainty  the  conditions  under  which  it  is  likely 
to  occur.  It  is  not  yet  possible  to  explain  how  it  is  produced,  what 
factors  underlie  its  occurrence,  what  the  vulnerable  points  in  the 
visual  mechanism  are,  nor  how  these  points  may  be  reached  or  pro- 
tected. In  order  to  increase  our  knowledge  concerning  these  im- 
portant questions,  the  prime  requisite  for  experimental  attack  is  a 
method  of  measuring  visual  fatigue.  And  up  to  the  present  time 
this  phenomenon  has  taken  very  unkindly  to  association  with  any 
form  of  yardstick. 

Since  visual  fatigue  as  a  whole  appears  at  present  impossible  of 
measurement,  the  only  alternative  open  is  the  measurement  of  the 
fatigue  of  the  various  individual  processes  involved  in  vision.  The 
physiological  characteristics  and  properties  of  the  different  tissues 
have  been  carefully  studied,  and  their  behavior  is  fairly  well  known. 
It  should  be  possible,  therefore,  by  determining  the  reactions  of  the 
individual  units  or  unit  functions  to  fatiguing  conditions,  to  deter- 
mine the  locations,  and  the  relative  amounts  of  fatigue  in  those 
locations,  and  their  proportions  to  the  sum  total  of  visual  fatigue. 

The  first  step  in  such  an  attack  is  therefore  the  subdivision  of  the 
visual  process  into  its  unit  functions  and  structures.  The  accom- 
panying classification  has  been  adopted  as  a  basis  for  the  study  of  the 
various  parts  of  the  visual  mechanism  as  they  individually  show 
themselves  subject  to  fatigue. 

The  responsibility  for  visual  fatigue  has  been  laid  at  the  door  of 
most  of  the  functional  groups  enumerated  above.  Many  of  these 
groups  have  been  studied  experimentally,  and  a  large  amount  of 
interesting  and  important  data  relative  to  the  occurrence  of  fatigue 
has  been  accumulated.  A  study  of  the  results  of  those  experiments 
becomes  an  integral  part  of  our  immediate  problem,  since  it  is  to 
those  findings  that  we  must  add  further  experimentation  in  order  to 
increase  the  factual  basis  leading  to  the  solution  of  our  problem. 

A  very  prevalent  idea  among  workers  on  the  subject  is  that  the 
extraocular  muscles  are  the  chief  offenders  in  the  establishment  of 
visual  fatigue.  A  moment's  consideration  will  bring  out  the  fact 
that  the  eyes  are  in  motion  almost  constantly  throughout  the  day, 
and  that  no  matter  what  the  occupation,  they  are  an  important  and 
ever-active  tool.  Luckiesh  and  Moss5  have  estimated  that  one- 
fourth  of  the  consumption  of  bodily  energy  is  due  to  seeing.  The 
number  of  motions  made  by  an  eye  in  an  average  day's  work  is  of 



[J.  S.  M.  P.  E. 

course  tremendous.  On  the  other  hand,  the  average  amount  of 
motion  performed  by  the  eye  does  not  result  in  sufficient  fatigue  to 
produce  perceptible  symptoms.  One  is  very  conscious,  for  example, 
of  fatigue  of  the  upper  arm  muscles  when  an  attempt  is  made  to 
hold  the  arms  outstretched  for  even  a  short  length  of  time.  In  all 
probability,  the  eye  muscles  are  of  sufficient  strength  to  care  for 
the  average  needs  of  ocular  motion  without  becoming  fatigued. 
It  is  necessary,  however,  to  examine  this  question  much  more  care- 

Functional  Group 
Effectors — the  mecha- 
nisms controlling 
change  in  the  physical 
modification  of  the  in- 
cident light  and  its 
relation  to  the  eye. 

2.  Receptors — the  mecha- 
nisms   bringing   about 
the  transposition  from 
physical  to  physiologi- 
cal stimulus. 

3.  Conductor s — t h e 
mechanisms     involved 
in   the   conduction    of 
the  physiological 
stimulus,  and  its  elabo- 
ration to  the  condition 
of    perception. 



a.  Accommodation    (lens 
changes  only) . 

b.  Diaphragmatic     func- 
tion of  the  iris. 

c.  Fixation. 

d.  Pigment  migration. 

e.  Movements    of    cones 
and  rods. 

A  natomical  Structures 

Ciliary  body  muscu- 

Iris,  constrictor,  and 
dilator  muscles. 

Extraocular  muscles. 

Hexagonal  cells  of  the 
retinal  epithelium. 

Cones  and  rods. 

a.  Irritability  to  light.         Rods  and  cones. 



and    per- 

Control  and  conduc- 
tion of  the  stimulus 
for  the  improvement  of 
perception  through  the 
effectors  of  group  1. 

Retina  (except  rods 
and  cones),  optic 
nerve,  and  brain. 

Various  cranial  nerves 
and  brain  centers. 

fully  in  order  to  decide  with  some  degree  of  probability  what  per- 
centage, if  any,  of  visual  fatigue  is  due  to  fatigue  of  the  extraocular 

Lancaster3  presents  an  analysis  of  the  work  done  by  the  extra- 
ocular  muscles.  He  points  out  that  they  are  much  more  favorably 
situated  in  regard  to  their  mechanical  advantage  than  are  the  other 
striated  muscles  of  the  body.  He  has  calculated  that  the  amount 
of  force  required  to  move  the  eye  through  an  arc  of  10  degrees  in 

May,  1933  ]          EXPERIMENTAL  STUDY  OF  VISUAL  FATIGUE  373 

0.04  second  is  equal  to  1.73  grams.  The  power  of  the  muscle  to 
overcome  this  load  is  equivalent  to  750-1000  grams,  so  that  there 
is  a  tremendous  latitude  between  reserve  force  and  actual  demand. 
It  is  difficult  to  fatigue  any  muscle  unless  it  is  made  to  work  against 
a  load  which  is  severe.  While  there  are  no  direct  studies  as  yet 
upon  extraocular  muscles,  it  is  highly  probable  that  such  a  study 
would  show  no  measurable  fatigue  of  these  muscles  under  a  load 
considerably  greater  than  their  average  load.  Under  normal  condi- 
tions the  extraocular  muscles  maintain  their  activity  indefinitely, 
by  a  mechanism  whereby  the  various  fibers  in  a  muscle  take  turns 
supporting  the  load  so  that  each  individual  fiber  works  for  but  a 
small  fraction  of  the  time;  thus  fatigue  does  not  occur. 

The  function  of  the  extraocular  muscles  is  that  of  fixation.  Lan- 
caster3 believes  that  fixation  is  one  of  the  two  functions  in  the  visual 
process  which  are  subject  to  fatigue.  The  process  of  fixation, 
however,  involves  other  structures  as  well  as  the  extraocular  muscles, 
which  serve  only  as  effectors.  Even  if  it  be  possible  to  justify  the 
argument  against  the  occurrence  of  fatigue  in  the  extraocular  muscles, 
there  still  remains  the  possibility  of  its  occurring  in  the  central 
mechanism  controlling  fixation. 

By  photographing  the  eye  movements,  the  process  of  fixation  has 
been  shown  to  take  place  in  two  stages :  first,  the  eyes  move  rapidly 
to  bring  the  object  being  fixated  in  the  center  of  the  field;  then, 
secondly,  slow,  delicate  movements  are  made  to  bring  the  image  of 
the  object  fixated  in  the  exact  spot  upon  the  retina  where  it  is  wanted. 
During  prolonged  fixation  upon  an  object,  there  is  a  constant  slight 
shifting  necessary  for  the  finest  perception  possible;  occasional 
gross  movements  also  occur  at  intervals  as  fixation  is  maintained. 

From  a  binocular  point  of  view,  fixation  has  a  latitude  which  is 
dependent  upon  Panum's  area.  Lancaster3  has  shown  that  in 
favorable  conditions,  as  in  fixating  objects  which  are  easy  to  see, 
the  eye  does  not  make  the  finest  adjustments  of  which  it  is  capable. 
The  ordinary  adjustments  required  of  the  eyes  are  not  very  accurate. 
However,  when  conditions  are  unfavorable  for  seeing,  as  with  poor 
print,  unsteady  light,  or  shiny  paper,  the  eye  must  adjust  more 
accurately  in  order  to  see  as  well.  There  is  then  a  greater  demand 
on  the  mechanism  for  fixation,  and  it  is  certainly  possible  that  under 
these  conditions  the  extraocular  muscles  as  well  as  the  mechanism 
for  fixation  may  contribute  to  ocular  fatigue. 

Ferree  has  offered  the  suggestion  that  light  striking  the  periphery 

374  PETER  A.  SNELL  [J.  S.  M.  P.  E. 

results  in  a  stimulus  tending  to  bring  about  fixation  of  the  light  source, 
with  consequent  turning  of  the  eyes  in  that  direction.  If  the  light 
persists  in  the  periphery  during  continued  fixation  of  the  former 
object,  the  rivalry  resulting  between  the  two  fixation  positions  is 
a  cause  for  the  production  of  fatigue  of  the  extraocular  muscles. 
Such  a  situation  frequently  arises.  It  is,  however,  rather  more  in 
line  with  usual  physiological  behavior  to  place  the  site  of  a  fatigue 
arising  as  the  result  of  such  a  situation  in  the  central  mechanism 
for  fixation,  rather  than  in  the  extraocular  muscles  themselves.  The 
rivalry  which  occurs  is  central;  the  muscles  can  not  be  fatigued  by 
the  possibility  of  activity  which  actually  does  not  occur. 

Howe7  has  made  a  study  of  fatigue  of  the  extraocular  muscles 
by  an  instrument  which  he  calls  the  ophthalmic  ergograph.  This 
instrument  consisted  essentially  of  a  variable  prism  whose  strength 
was  automatically  recorded.  It  was  found  that  the  strength  of  the 
prism  which  the  various  muscles  could  overcome  by  their  action 
decreased  during  successive  attempts  over  a  given  length  of  time. 
Experiments  such  as  these  are  interesting  in  showing  the  amount 
of  effort  necessary  to  elicit  fatigue;  they  do  not  localize  the  site  of 
that  fatigue.  If  the  prism  is  so  arranged  that,  for  example,  adduc- 
tion is  shown  to  become  fatigued,  this  fatigue  may  occur  either  in 
the  adductor  muscles,  or  in  the  central  mechanism  for  their  control, 
and  in  the  mechanism  for  fusion  of  the  two  images.  By  the  nature 
of  the  experiment,  none  of  these  possibilities  are  excluded. 

It  is  justifiable  to  conclude  that  the  evidence  so  far  presented 
indicates  that  fixation  plays  only  a  small  role  in  general  visual 
fatigue,  and  that  it  is  the  central  or  nervous  part  of  the  mechanism, 
rather  than  the  extraocular  muscles  themselves,  which  is  the  vul- 
nerable spot  in  the  fixation  process. 

Accommodation  has  frequently  been  accused  of  much  responsi- 
bility in  the  occurrence  of  ocular  fatigue.  It  is  common  knowledge 
that  those  who  are  inclined  to  suffer  following  visual  overwork  fre- 
quently lay  the  blame  on  reading  and  other  forms  of  close  work, 
which  differ  from  distance  vision  in  the  necessity  for  prolonged 
accommodation.  Accommodation,  therefore,  appears  directly  re- 
sponsible. According  to  the  generally  accepted  theory  regarding 
the  mechanism  of  accommodation,8  the  ciliary  muscle  is  under  a 
greater  tension  when  the  surface  of  the  lens  is  adjusted  to  bring  the 
image  of  near  objects  to  a  focus  upon  the  retina;  it  is  more  relaxed, 
or  under  less  tension,  when  the  eye  is  accommodated  for  far  objects. 


This  condition  has  led  students  of  the  problem  to  consider  seriously 
the  possibility  that  prolonged  accommodation  for  near  objects  can 
be  fatiguing  on  account  of  the  prolonged  increased  tension  which 
must  necessarily  be  maintained  by  the  ciliary  muscle.  In  connection 
with  accommodation,  the  convergence  of  the  eyes  for  binocular 
vision  introduces  the  problem  of  fatigue  of  the  extraocular  muscle 
system  into  this  question. 

Berens  and  Stark9  made  an  excellent  study  of  accommodation 
fatigue  using  an  improved  form  of  ergograph.  Their  findings, 
contrary  to  those  of  Howe,  indicated  that  it  was  not  usual  to  observe 
recession  of  the  near  point  and  decrease  in  amplitude  of  excursion 
within  the  time  limit  used.  These  experiments  are  extremely 
interesting  in  that  they  show  that  under  much  more  severe  use  than 
is  customary,  the  mechanism  for  accommodation  does  not  break 
down.  It  is  not  unlikely,  however,  that  within  this  mechanism 
the  principle  of  compensation  is  responsible  for  failure  to  demonstrate 
a  breakdown.  It  is  a  well-known  fact  that  the  ciliary  body  is  over- 
developed in  eyes  whose  refraction  is  hyperopic,  and  that  in  these 
people  eye-strain  is  a  fairly  common  complaint;  on  the  other  hand, 
individuals  with  myopic  eyes,  which  have  an  underdeveloped  ciliary 
body,  seldom  complain  of  ocular  pain.  The  association  of  these 
facts  can  not  be  interpreted  otherwise  than  as  an  indication  that  the 
mechanism  of  accommodation  and  the  ciliary  body  are  far  from 
blameless  in  the  production  of  ocular  fatigue. 

The  diaphragmatic  function  of  the  iris  enters  into  the  process  of 
accommodation.  The  narrowing  of  the  pupil  in  this  connection 
has  for  its  purpose  the  improvement  of  the  image  by  cutting  off 
the  rays  from  the  peripheral  and  less  perfect  regions  of  the  refracting 
media.  It  is  a  point  of  interest  that  this  constriction  of  the  pupil 
is  at  the  same  time  deleterious  to  the  accuracy  of  the  image  because 
of  the  proportionate  increase  in  the  amount  of  diffraction  occurring 
around  the  margins  of  the  pupil.  Cobb10  has  shown  that  at  a  pupil 
diameter  of  about  4  mm.  the  eye  is  at  its  maximum  optical  accuracy. 

There  are  so  many  unknown  quantities  in  connection  with  ac- 
commodation that  it  is  far  too  early  to  estimate  with  any  degree  of 
probability  its  proportion  of  responsibility  in  visual  fatigue.  The 
variables  of  lens  changes,  iris  activity,  and  convergence  function, 
not  to  mention  some  unsolved  questions  concerning  the  mechanism 
for  bringing  about  the  lens  changes,  all  contribute  to  the  difficulty 
of  an  attack  upon  the  problem. 

376  PETER  A.  SHELL  [j.  s.  M.  P.  E. 

Accommodation,  moreover,  can  not  be  ruled  out  of  motion  picture 
fatigue  on  the  ground  that  near  vision  is  not  involved,  since  hy- 
peropia  is  such  a  common  refractive  error  of  mankind.  In  general, 
however,  the  conditions  present  in  the  theater  are  such  that  very 
little  is  demanded  of  accommodation.  Therefore,  although  it  is 
impossible  at  present  to  make  any  really  reasonable  prediction 
about  accommodative  fatigue,  it  is  justifiable  to  adopt  for  the  present 
purpose  the  assumption  that  fatigue  from  accommodation  is  not 
important  in  ocular  fatigue  resulting  from  viewing  the  motion 

The  diaphragmatic  function  of  the  iris  in  controlling  the  amount 
of  light  reaching  the  retina  is  next  to  be  considered.  It  is  the  ex- 
perience of  every  one  that  on  passing  from  a  dark  environment  out 
into  the  much  brighter  sunlight,  a  rather  severe,  sharp  ocular  pain 
occurs.  Dr.  Fuchs  was  interested  in  the  part  which  the  iris  mecha- 
nism might  play  in  this  reaction;  he  performed  the  experiment  of 
comparing  the  sensations  experienced  upon  passing  from  the  dark 
into  brilliant  light  when  his  pupils  were  dilated  with  scopolamine 
and  when  they  were  not  under  the  effect  of  the  drug.  In  the  former 
case  he  found  that  no  pain  was  experienced  in  spite  of  the  fact  that 
much  more  light  reached  the  retina;  he  logically  attributed  the 
difference  in  sensation  to  the  fact  that  the  pupil  did  not  react  when 
under  the  influence  of  the  drug,  and  concluded  that  it  was  the  violent 
contraction  of  the  pupil  which  was  responsible  for  the  pain  experi- 
enced. This  is  an  extremely  interesting  observation.  The  fully 
contracted  pupil  is  obviously  not  painful;  no  pain  is  experienced 
once  the  adaptation  to  the  most  brilliant  sunlight  is  complete. 
What  is  it  then  that  is  painful? 

Michaelson11  has  presented  in  connection  with  an  analysis  of  100 
cases  of  ocular  headache,  a  discussion  of  the  nervous  innervation 
of  the  iris  and  ciliary  body.  He  has  pointed  out  an  analogy  be- 
tween this  system  and  that  of  various  other  organs  in  the  body  which 
are  grouped  together  by  Head12  as  visceral-sensory  mechanisms. 
Michaelson  comes  to  the  conclusion  that  ciliary  headache  is  the  chief 
type  of  ocular  headache,  and  that  the  structures  involved  are  analogous 
to  those  which  give  rise  to  referred  visceral  pain  in  other  parts  of 
the  body.  In  the  production  of  visceral  pain,  distension  is,  in  prac- 
tically all  cases,  the  adequate  stimulus.  It  is  natural,  therefore, 
to  assume  distension  as  the  adequate  stimulus  for  ciliary  pain.  The 
analogy,  however,  is  not  perfect.  The  pupil  is  not  distended  when 

May,  1933  ]          EXPERIMENTAL  STUDY  OF  VISUAL  FATIGUE  377 

dilated;  it  is  under  conditions  exactly  resembling  distension  when, 
dilated,  it  is  receiving  stimuli  for  contraction.  From  Dr.  Fuch's 
experiment  it  is  evident  that  these  are  exactly  the  conditions  which 
produce  pain.  It  is  justifiable  to  suspect  the  occurrence  of  perhaps 
less  conscious  visceral-sensory  pain  stimuli  under  any  condition 
which  involves  the  production  of  stimuli  for  decrease  in  pupillary 
size  or  contraction  of  the  ciliary  muscles.  In  general,  any  condition 
leading  to  increased  difficulty  in  seeing  involves  the  production  of 
stimuli  for  ciliary  activity  and  pupillary  constriction  in  order  to 
improve  the  image;  consequently,  difficult  seeing  becomes  by  this 
mechanism  an  adequate  stimulus  for  the  causation  of  ocular  dis- 
comfort and  pain. 

The  above  considerations  lend  themselves  in  part  to  experimental 
verification.  Using  a  method  similar  to  that  of  Reeves,13  it  should 
be  possible  to  study  the  relationship  of  pupillary  changes  to  difficult 
visual  conditions.  I  hope  shortly  to  be  able  to  undertake  such  a 

Pigment  migration  and  movements  of  rods  and  cones  can  be 
grouped  together  under  the  statement  that  it  is  not  known  how 
important  a  role  these  functions  play  in  whatever  part  of  the  visual 
process  they  may  be  concerned.  The  chief  function  of  these  move- 
ments is  probably  concerned  with  the  adaptation  of  the  retina  to 
different  brightness  levels.  Arey14  has  made  some  studies  on  the 
question  of  control  of  pigment  migration,  and  has  found  that  in 
some  animals  it  is  easy  to  demonstrate  a  central  nervous  control  of 
the  activity,  while  in  other  cases  the  demonstration  is  not  so  easy. 
The  significance  of  the  movements  is  also  not  well  understood. 
Arey  interprets  them  as  protoplasmic  responses  to  definite  stimulat- 
ing agents.  With  the  mechanism  and  purpose  of  these  functions 
so  much  in  doubt,  consideration  of  them  must  necessarily  be  post- 
poned. If  they  play  any  part  in  visual  fatigue  the  magnitude  of 
their  share  can  not  be  estimated. 

The  question  of  retinal  fatigue  is  one  which  has  until  recently  not 
received  much  consideration  by  investigators.  Its  importance, 
however,  has  not  been  unrecognized.  Jackson4  says,  "Fatigue  of 
the  retina  and  visual  centers  is  more  important  than  all  other  func- 
tions connected  with  vision."  There  has  as  yet  been  no  direct 
attempt  made  to  measure  retinal  fatigue,  but  there  are  numerous 
instances  in  the  literature  of  fatigue  of  the  retinal  and  central  type 
occurring  in  the  course  of  a  study  upon  some  phase  of  the  visual 

378  PETER  A.  SNELL  [j.  S.  M.  P.  E. 

process.  Luckiesh  and  Moss15  cite  an  experiment  in  which  the  rate 
of  working  was  measured  when  the  visual  task  set  involved  a  fre- 
quent change  from  light  of  one  intensity  to  that  of  another.  The 
experiment  brought  out  the  loss  in  work  done  incident  to  the  time 
required  for  the  frequent  readaptation,  and  incidentally  demon- 
strated that  such  a  situation  was  productive  of  a  severe  eye  fatigue 
as  experienced  by  the  subjects. 

It  is  a  well-known  fact  that  contrasts  are  fatiguing.  Jackson4 
believes  that  contrast  is  one  of  the  most  important  sources  of  fatigue, 
and  states  that  "retinal-central  fatigue  is  increased  by  great  differ- 
ence in  intensity  of  stimulus  to  which  adjoining  parts  of  the  retina 
are  subjected."  Contrast  is  a  phenomenon  involving  many  factors, 
including  not  only  external  conditions,  but  also  sensory,  retinal,  and 
central  nervous  system  functions.  Granit16  has  recently  pointed 
out  that  there  is  a  retinal  component  in  contrast,  and  thereby  has 
added  a  further  indication  toward  the  probability  that  the  effect 
of  contrast  in  producing  fatigue  lies  in  the  retinal-central  mechanism. 

Flicker  is  a  phenomenon  closely  allied  to  contrast.  Fatigue 
results  as  readily  from  exposure  to  flicker  as  from  exposure  to  simul- 
taneous contrasts.  While  flicker  has  been  studied  very  thoroughly 
and  the  phenomenon  frequently  utilized  in  the  study  of  visual 
processes,  no  definite  explanation  has  been  forthcoming  for  the 
vulnerability  of  the  eye  to  this  form  of  stimulation.  Lancaster3 
advanced  the  suggestion  that  the  basis  of  fatigue  from  flicker  was 
the  ineffectual  attempt  of  the  eye  to  produce  a  steady  flux  of  energy 
upon  the  retina ;  the  inability  of  the  effector  mechanism  to  transform 
a  flickering  stimulus  into  a  steady  flux  resulted  in  rapid  fatigue  of 
that  mechanism.  While  such  a  process  is  important,  it  can  not  be 
considered  as  more  than  simply  contributory  to  contrast  fatigue; 
in  the  light  of  recent  work  it  appears  that  the  retinal  factor  is  the 
most  important. 

While  contrast  fatigue  is  not  the  only  form  of  retinal  fatigue,  it 
is  by  far  the  most  important,  and  the  most  representative  of  retinal 
behavior.  The  retina  as  a  sense  organ  is  peculiar  in  that  adaptation 
plays  a  larger  role  in  its  function  than  in  that  of  any  other  organ. 
Consequently,  the  retina  is  not  suited  for  a  quantitative  interpreta- 
tion of  stimulation.  It  is  commonly  said  that  the  "eye  can  equate 
but  can  not  appraise."  If  contrasts  were  entirely  removed  from 
our  field  of  vision,  it  would  be  almost  impossible  for  the  eye  to  de- 
termine whether  our  surroundings  were  bright  sunlight  or  total 

May,  1933]          EXPERIMENTAL  STUDY  OF  VISUAL  FATIGUE  379 

darkness.  The  study  of  contrast  behavior  is  thus  the  most  im- 
portant method  of  studying  visual  function. 

The  recent  studies  of  Granit16  and  others  have  emphasized  the 
importance  of  the  peripheral  or  retinal  share  in  the  analysis  of  visual 
sensation,  and  have  helped  to  focus  attention  upon  the  retina  as 
playing  probably  a  much  greater  part  in  the  analysis  and  inter- 
pretation of  impulses  coming  from  the  sense  endings  than  has  hitherto 
been  suspected.  Sir  John  Parsons,17  in  1925,  pointed  out  the  in- 
creasing evidence  for  complexity  of  retinal  behavior,  and  stated 
that  the  duplicity  theory  would  prove  to  be  too  great  a  simplification 
of  retinal  physiology.  The  newer  work  is  amply  bearing  out  his 

In  the  light  of  the  new  knowledge  of  retinal  function,  the  question 
of  fatigue  occurring  in  this  organ  becomes  one  of  unusual  interest. 
In  the  course  of  the  present  study,  it  appeared  that  of  the  many 
phases  of  the  problem  of  visual  fatigue  awaiting  experimental  attack, 
none  was  as  important  as  that  of  the  part  played  by  the  retina  in 
general  visual  fatigue.  The  experimental  work  was  therefore 
planned  as  an  attack  upon  the  problem  of  demonstrating  the  oc- 
currence of  retinal  fatigue,  together  with  an  attempt  to  estimate 
quantitatively  its  importance  as  compared  with  fatigue  of  other 
parts  of  the  visual  mechanism. 


In  the  last  ten  years  there  have  been  many  advances  made  in  our 
knowledge  of  the  behavior  of  sense  organs  in  general.  Adrian19 
has  shown  that  all  forms  of  peripheral  sensitivity  depend  on  func- 
tional units  whose  behavior  is  basically  similar.  For  the  sense  of 
sight,  he  has  shown  that  this  basic  behavior  is  modified  so  that  the 
demonstrable  changes  in  the  eye  and  optic  nerve  are  complicated 
by  the  interposition  of  the  retina;  therefore  he  was  able  to  study  the 
part  played  by  the  retina  in  the  elaboration  of  the  stimuli  from  the 
light  sense  endings.  Granit18  demonstrated  that  phenomena  char- 
acteristic of  central  nervous  system  behavior  could  be  shown  to  occur 
in  the  retina,  and  that  therefore  the  retina  could  properly  be  called 
a  true  nervous  center.  The  experimental  work  of  Adrian  and  Granit 
on  the  eyes  affords  a  basis  for  the  experimental  attack  on  the  question 
of  retinal  fatigue. 

Adrian  showed  in  his  studies  on  the  eel's  eye  that  the  total  effect 
of  light  falling  on  the  eye  was  transmitted  to  some  region  whose 

380  PETER  A.  SNELL  [j.  S.  M.  P.  E. 

extent  was  independent  of  the  area  illuminated.  In  addition,  he 
found  that  under  certain  conditions  a  rhythmical  discharge  occurred 
in  the  optic  nerve  as  a  result  of  action  in  unison  of  the  ganglion 
cells  in  the  retina.  Furthermore,  he  showed  that  when  four  separated 
regions  on  the  retina  were  illuminated  simultaneously,  the  reaction 
time  was  shorter  than  when  one  was  illuminated  alone;  this  inter- 
action between  distant  retinal  areas  was  enhanced  by  the  addition 
of  strychnine  to  the  prepared  anatomical  specimen,  a  drug  which  by  its 
action  decreases  synaptic  resistance.  These  experiments,  therefore, 
demonstrated  among  other  findings  the  presence  of  an  interaction 
taking  place  in  the  retina  as  a  fundamental  part  of  its  reaction  to 
simple  stimuli. 

Granit16  demonstrated  the  occurrence  of  interaction  in  the  human 
eye  by  adapting  Adrian's  experiment  to  a  subjective  method.  Using 
critical  frequency  as  a  criterion  for  the  effective  intensity  of  a  stimu- 
lus, he  showed  that  the  effective  intensity  of  a  given  stimulus  was 
lower  when  the  stimulus  was  presented  alone  than  when  presented 
simultaneously  with  stimuli  falling  on  other  parts  of  the  retina. 
In  further  experiments  he  studied  the  relationship  of  interaction 
to  retinal  behavior,  and  showed  that  many  of  the  properties  of  the 
visual  mechanism  were  bound  up  with  retinal  reactions  of  the  synap- 
tic type. 

Granit  considers  that,  for  any  given  amount  of  activity  in  a  func- 
tioning group  of  ganglion  cells,  part  of  this  activity  results  from 
activity  beginning  in  receptors  directly  in  front  (distal)  of  the  gang- 
lion cells,  and  part  is  the  result  of  activity  coming  via  association 
fibers  from  sense  endings  lateral  to  the  active  cells.  Any  given  spot 
of  activity  in  the  ganglion  cells  thus  has  an  effective  intensity  which 
represents  the  sum  of  input  over  frontal  and  lateral  channels.  By 
the  proper  selection  of  differing  types  of  stimulus,  therefore,  it  is 
possible  to  distinguish  between  frontal  and  summative  responsibility 
for  changes  in  effective  intensity.  Granit  demonstrated  by  this 
method  that  the  site  of  adaptation  lay  in  the  sense  endings  rather 
than  in  the  synaptic  mechanism. 

This  method  is  well  suited  to  the  purpose  of  localizing  the  oc- 
currence of  retinal  fatigue.  By  its  use  it  should  be  possible  not  only 
to  determine  whether  any  fatigue  occurs  in  the  retina,  but  also  to 
assign  a  semi-quantitative  value  to  the  various  factors  concerned 
in  the  causation  of  the  fatigue. 

The  apparatus  finally  adopted  was  a  compromise  between  the 



ideal  and  one  which,  while  suited  to  the  various  types  of  experiment, 
could  be  constructed  with  the  minimum  of  delay.  As  a  source  of 
illumination,  a  standard  projection  lamp  was  used,  mounted  in  a 
suitable  lamp  house.  The  optical  system  consisted  of  the  usual 
condenser  lenses  and  projection  lens,  so  arranged  that  the  plane  of 
the  image  of  the  lamp  filament  was  a  few  centimeters  in  front  of  the 
projection  lens.  In  this  plane  was  placed  a  rotating  sector  disk, 
so  that  when  the  sector  disk  was  rotating,  movements  of  the  image 
of  the  diaphragm  on  the  screen  were  negligible.  The  arrangement 
is  illustrated  in  Fig.  1.  The  size  and  shape  of  the  image  on  the 


NOV.  D.C. 

FIG.  1.  Diagram  illustrating  the  apparatus  used  for  determining  ocular 
fatigue:  1,  lamp  control  resistance ;  2,  lamp  circuit  ammeter;  3,  lamp  cir- 
cuit voltmeter;  4,  projected  slit;  5,  sector  disk;  6,  disk  motor  control  re- 
sistance; 7,  Western  Electric  tachometer;  8,  tachometer  voltmeter ;  9,  screen; 
10,  subject. 

screen  were  controlled  by  the  use  of  different  diaphragms;  the 
intensity  of  illumination  was  varied  by  a  resistance  in  the  lamp 
circuit.  This  method  is  sufficiently  accurate  for  the  comparatively 
narrow  range  over  which  the  variations  were  made.  The  actual 
intensity  on  the  screen  was  measured  for  the  different  lamp  amperages 
with  a  Macbeth  illuminometer. 

In  actual  practice,  the  subject  was  seated  20  feet  from  the  screen. 
A  preliminary  period  of  adaptation  to  a  very  low  level  of  illumina- 
tion, lasting  20  minutes,  preceded  every  experiment.  Both  eyes 
of  the  subject  were  always  exposed  to  the  fatiguing  stimulus;  the 
critical  frequency  determinations  were  made  on  the  right  eye.  In 
taking  the  readings,  an  attempt  was  made  to  obtain  the  point  at 
which  flicker  just  appeared  in  at  least  6  seconds,  since  this  is  con- 
sidered the  approximate  length  of  time  during  which  the  eye  can 



[J.  S.  M.  P.  E. 

fixate  a  given  point  without  moving.  If  more  than  6  seconds  proved 
necessary,  the  reading  could  usually  on  the  next  attempt  be  made 
within  that  time,  since  the  approximate  value  was  then  known. 
The  speed  of  rotation  of  the  sector  disk  was  varied  by  a  resistance 
in  the  armature  circuit  of  the  motor,  and  the  rpm.  indicated  by  a 
Weston  tachometer.  One  sector  disk  was  used  for  all  the  critical 
frequency  readings. 

The  experiments  were  begun  by  determining  the  critical  frequency 
curves  for  the  normal  eye.  The  curves  were  plotted  for  only  two 
different  areas  of  stimulation,  since  these  two  are  all  that  are  neces- 
sary. Fig.  2  shows  the  curves  of  four  subjects  for  a  stimulation  area 











FIG.  2. 

.8  1.2 

LOG.  OF  I 

Critical  frequency  curves  for  four  subjects,  for  stimulation  area  of 
four  degrees'  diameter. 

of  4  degrees  of  diameter;  there  is  apparent  a  marked  difference  in 
sensitivity  to  flicker  between  different  individuals,  though  all  sub- 
jects show  the  usual  logarithmic  relationship  between  intensity  and 
critical  frequency. 

The  critical  frequency  for  any  given  stimulation  varies  not  only 
with  the  condition  of  the  eye  as  a  result  of  previous  activity  of  the 



eye,  but  also  with  the  general  condition  of  the  subject.  It  was 
found  that  in  order  to  obtain  reproducible  results,  it  was  necessary 
to  demand  of  the  subjects  that  they  always  retire  early  the  evening 
before,  and  that  they  do  no  reading  before  coming  to  the  laboratory 
the  next  morning.  Not  more  than  two  hours  could  be  utilized  in 
any  one  day,  since  readings  made  over  a  longer  period  of  time  or  in 
the  afternoon  showed  greater  variability  than  those  taken  in  the 
early  part  of  the  day. 

The  method  for  demonstrating  and  localizing  the  retinal  fatigue 






A^-4  — 



LOG.  OF  I 



FIG.  3.     Critical  frequency  curves  derived  from  the  curves  of  Fig.  2,  for  dem- 
onstrating the  localizing  of  retinal  fatigue. 

depends  on  the  fact  that  interaction  plays  a  proportionately  greater 
role  in  bringing  about  a  given  effective  intensity  as  the  area  of  the 
retina  stimulated  is  increased.  From  the  critical  frequency  curves 
of  the  subject,  three  points  are  chosen,  as  shown  in  Fig.  3.  These 
points  are  so  related  that  points  A  and  C  have  the  same  area  but 
different  intensities,  C  and  B  the  same  critical  frequency  (effective 
intensity)  but  different  areas,  and  A  and  B  the  same  intensity  but 

384  PETER  A.  SNELL  [j.  S.  M.  P.  E. 

different  areas.  C  has  the  same  critical  frequency  as  B  in  spite  of  its 
lower  intensity,  because  of  its  greater  amount  of  interaction.  A  owes 
a  larger  percentage  of  its  effective  intensity  to  interaction  than  does 
B,  because  of  its  larger  area. 

In  practice,  the  subject  observed  the  screen  for  half  an  hour, 
while  a  slowly  flickering  light  was  projected  thereon.  During  the 
half  hour,  five  readings  of  the  critical  frequency  were  taken  for  one 
of  the  three  "crucial  points,"  A,  B,  or  C;  the  points  were  presented 
either  at  random  or  in  rotating  order.  Half-hour  runs  were  also 
made  with  readings  for  the  same  point  taken  throughout.  No  read- 
ing was  ever  taken  at  twenty-five  minutes  in  order  to  avoid  any  effect 
on  the  value  at  thirty  minutes,  although  it  was  found  that  the  break 
in  the  fatiguing  stimulus  necessary  to  take  a  critical  frequency  read- 
ing had  a  negligible  effect  on  the  subsequent  readings.  Since  many 
experiments  were  therefore  necessary  to  obtain  the  essential  data, 
those  points  for  which  one  check  was  obtained  were  included  in  the 
results;  it  would  be  better  from  a  statistical  point  of  view  to  include 
many  readings  and  calculate  the  mean  of  the  values  obtained,  but 
time  was  not  available.  Moreover,  a  more  exact  determination  of 
the  absolute  values  for  the  critical  frequency  is  superfluous  in  view 
of  the  fact  that  other  variables  in  the  factors  involved  in  the  ex- 
periment can  not  be  controlled  within  a  variability  range  as  small  as 
that  represented  by  the  values  for  critical  frequency  obtained  by 
the  above  method. 

The  analysis  of  the  readings  is  shown  in  Fig.  4.  For  each  of  the 
three  "crucial"  points  a  curve  is  plotted  showing  the  course  of  the 
critical  frequency  change  with  time.  On  the  same  graph  is  plotted 
a  curve  obtained  in  exactly  the  same  manner  as  the  first  except  that 
the  "fatiguing"  stimulus  was  not  flickering.  The  difference  between 
the  two  curves  represents  the  fall  in  effective  intensity  resulting  from 
the  flicker  characteristic  of  the  stimulus.  It  therefore  represents 
a  true  flicker  fatigue. 

Table  I  presents  a  summary  of  the  results  for  the  three  subjects 
upon  whom  a  complete  set  of  readings  was  obtained.  Subject 
T.N.  showed  the  greatest  susceptibility  to  flicker  fatigue.  The 
table  shows  that  in  one-half  hour  point  A  fell  to  an  effective  intensity 
of  10  per  cent  of  the  original  value;  while  at  the  same  time  points 
B  and  C  fell  to  30  and  28  per  cent,  respectively,  of  their  former 
levels.  Thus  A ,  with  the  largest  proportion  of  its  effective  intensity 
due  to  interaction,  fell  the  most;  C  and  B,  with  relatively  much 



less  of  their  effective  intensity  due  to  interaction,  C  because  of  less 
intensity  than  A,  and  B  because  of  less  area,  have  fallen  much  less. 
The  other  subjects  show  the  same  relationship  between  the  three 





UJ  Ar\ 



\       4>               i 










10        20        30 




tf  *K 

uj  35 










1  < 
.  ARE; 


HIGH  ir 



10       20       30 














—  C- 


T^                 f 

)W  IN 

—  ^^—  —  —  < 

:  ARE 



10        20      30 


FIG  .  4.  Analytical  curves  showing  the 
change  of  critical  frequency  with  time; 
one  curve  for  each  of  the  "crucial" 
points  of  Fig.  3. 

points,  although  not  quite  to  the  same  degree.  Therefore,  it  can 
be  concluded  that  flicker  fatigue  takes  place  in  the  retinal -structures 
behind  the  sense  endings  rather  than  in  the  sense  endings  themselves. 

386  PETER  A.  SNELL  [j.  s.  M.  P.  E. 


Summary  of  Experiments  on  Localization  of  Retinal  Fatigue 

Per  Cent  of 












V*  Hr. 


V«  Hr. 



























H.B.  A  4          High        44.6        40.0         19.1          7.6          39 

B  1          High        37.3        34.6         19.1         11.0          57 

C  4          Low         37.3        34.0          4.6          2.5          54 

P.S.  A  4          High        53.0        41.3        42.0          7.2          17 

B  1          High       41.3        36.0        42.0        11.0          26 

C  4          High       41.3        33.3          7.6          2.3          30 

The  percentages  given  above  represent  definite  values  only  for 
a  given  experiment.  While  they  serve  to  differentiate  quite  clearly 
between  the  possible  sites  involved  in  the  reaction,  they  are  in  no 
wise  to  be  considered  as  representing  the  absolute  value  for  the  fatigue 
occurring  at  that  site.  It  is  not  yet  possible  to  estimate  the  absolute 
percentage  of  frontal  and  lateral  contributions  to  the  effective  in- 
tensity of  any  excited  area.  Moreover  the  location  of  the  stimulated 
area  is  of  importance  in  determining  the  amount  of  interaction  in 
the  response.  Therefore,  the  figures  obtained  represent  only  a 
semi-quantitative  value  for  the  local  fatigue;  they  nevertheless 
demonstrate  clearly  the  occurrence  of  retinal  flicker  fatigue  and  fix 
the  responsibility  for  most  of  it  upon  the  synapses. 

Table  II  shows  the  effect  of  rate  of  flicker  in  the  fatiguing  stimulus 
upon  the  effective  intensity.  Not  enough  data  were  obtained  to 
draw  any  very  definite  conclusions,  but  it  is  evident  that  as  long  as 
flicker  is  apparent  fatigue  occurs.  When  the  rate  of  flicker  is  such 
that  it  is  not  apparent,  there  is  no  fall  in  critical  frequency  during 
the  half-hour  period. 


The  Effect  of  Rate  of  Fatiguing  Flicker  upon  Effective  Intensity 
Rate  of  stimulus  13 . 3  26 . 6  53 . 3 

C.F.  E.I.  C.F.  E.I.  C.F.          E.I. 

Before  exposure  40.6         10.0  40.6         10.0  40.6       10.0 

After  Y2  hour  34.0          2.9  34.6          3.17  40.6       10. 0 

May,  1933  ]          EXPERIMENTAL  STUDY  OF  VISUAL  FATIGUE  387 


The  fact  that  fatigue  from  flicker  depends  on  the  perception  of 
the  flicker  rather  than  upon  the  absolute  rate  of  alternation  is  ex- 
tremely important.  These  two  factors  are  of  course  intimately 
related;  the  preliminary  experiments  show,  however,  that  it  is  the 
subject's  sensitivity  to  flicker  which  will  determine  whether  fatigue 
results  from  exposure  to  a  given  flickering  stimulus.  This  finding 
is  related  to  the  fact  brought  out  by  Grunbaum20  that  it  is  the  ratio 
of  time  of  constancy  of  stimulus  to  time  of  changing  stimulus  which 
has  the  greatest  effect  on  the  absolute  value  of  the  critical  frequency 
rather  than  the  rate  of  rotation  of  the  sector  disk.  No  attempt  was 
made  in  these  experiments  to  explore  the  relationship  between 
flicker  fatigue  and  sector  dimensions;  it  is  probable  that  the  rela- 
tionship will  be  found  to  be  closely  parallel  to  that  of  perceptibility 
of  flicker  with  sector  dimensions. 

The  curves  showing  the  relation  of  effective  intensity  changes  to 
exposure  to  non-flickering  light  indicate  that  very  little  effect  resulted 
from  such  a  stimulus.  This  relationship  is  a  consequence  of  the 
conditions  under  which  the  experiment  was  performed.  Lythgoe 
and  Tansley21  have  recently  brought  out  the  fact  that  during  ex- 
posure to  light  the  critical  frequency  due  to  rod  activity  falls,  while 
that  due  to  cones  rises.  The  type  of  response  is  determined  by  the 
illumination  level  of  the  surroundings.  In  these  experiments,  the 
background  illumination  level  and  the  size  of  the  screen  were  such 
that  very  little  change  in  adaptation  level  occurred.  Some  of  the 
curves  do  show  a  slight  tendency  toward  an  increase  in  the  critical 
frequency  during  exposure  to  the  steady  stimulus,  which  is  the  type 
of  change  to  be  expected  since  the  experimental  conditions  are  such 
that  cone  responses  are  chiefly  concerned. 

Flicker  is,  of  course,  not  the  only  environmental  condition  which 
elicits  retinal  fatigue.  Any  type  of  stimulus  will  bring  about  the 
same  kind  of  retinal  fatigue  in  proportion  to  the  amount  of  synaptic 
activity  involved  in  the  retinal  response.  The  ordinary  activities 
of  every-day  life  all  produce  a  certain  amount  of  retinal  fatigue  which 
can  be  detected  by  the  method  used  in  this  investigation.  When  one 
of  the  subjects  inadvertently  read  the  morning  newspaper  before 
coming  to  the  laboratory,  the  absolute  critical  frequency  levels  were 
depressed  more  than  10  per  cent.  Another  subject  made  the  mistake 
of  spending  some  time  in  drawing,  with  the  result  that  this  more 
severe  visual  task  left  his  retina  in  a  measurably  depressed  state 

388  PETER  A.  SNELL  [j.  s.  M.  p.  E. 

more  than  three  hours  afterward.  The  depression  of  retinal  response 
by  normal  activity  is  a  real  fatigue  in  the  physiological  sense;  the 
fatigue  must  progress  close  to  the  point  of  exhaustion  before  it  can 
intrude  into  consciousness  and  cause  symptoms. 

Finally,  it  may  be  profitable  to  consider  briefly  the  present  status 
of  the  question  in  connection  with  the  motion  picture.  As  a  visual 
task,  viewing  the  motion  picture  is  essentially  similar  to  all  other  visual 
tasks;  the  amount  of  involvement  of  the  various  functions  of  the 
visual  process  is  modified  by  the  factors  of  discontinuous  stimulation, 
dark  adaptation,  and  continuous  accommodation  for  far  incident 
to  this  particular  form  of  visual  work.  The  high  degrees  of  contrast 
present  and  the  discontinuous  nature  of  the  stimulus  have  both 
been  shown  to  be  important  causes  of  retinal  fatigue  and  consequent 
decrease  in  ability  to  see. 

In  Table  III  is  presented  an  estimate  of  the  relative  importance  of 
the  various  functions  of  the  visual  process  involved  in  motion  picture 
fatigue.  The  figures  are  to  be  considered  as  representing  only  the 
probable  values;  they  are  not  based  on  any  accurate  quantitative 


Estimate  of  the  Probable  Proportions  of  Responsibility  of  the  Functions  of  the  Visual 
Process  in  the  Production  of  Visual  Fatigue  by  the  Motion  Picture 

Function  Per  Cent 

Accommodation  (lens)  10 

Diaphragmatic  function  of  the  iris  10 

Fixation  10 

Pigment  migration  and  movements  of  rods  and  cones  0  (?) 

Irritability  to  light  (including  adaptation)  5 
Conduction  and  perception 

a.  Retinal  40 

b.  Central  15 
Control  of  effectors  10 

experiments,  and  are  presented  in  the  nature  of  a  summary  of  the 
above  discussion.  The  retina  has  been  shown  to  be  particularly 
susceptible  to  contrast  fatigue,  especially  perceptible  flicker.  The 
effectors,  particularly  those  of  the  uveal  tract,  are  unable  to  improve 
the  image  sufficiently  to  compensate  for  the  decreased  efficiency  of 
the  retina;  it  has  been  shown  that  there  probably  exists  a  mechanism 
for  translating  the  futile  excessive  efforts  of  the  effectors  into  un- 
comfortable sensations  and  even  pain.  As  long  as  the  fatigue  can 
be  kept  within  the  usual  limits  of  other  every-day  visual  tasks,  the 

May,  1933]          EXPERIMENTAL  STUDY  OF  VISUAL  FATIGUE  389 

existence  of  the  fatigue  will  not  make  itself  known.  When  this  is 
the  case,  viewing  the  motion  picture  will  be  no  more  fatiguing  than 
any  other  activity  of  the  organs  of  sight. 


This  work  was  carried  out  under  a  fellowship  of  the  Society  of 
Motion  Picture  Engineers  at  the  Institute  of  Applied  Optics,  Uni- 
versity of  Rochester.  I  am  deeply  indebted  to  the  members  of  the 
staff  for  their  valuable  assistance  and  cooperation  during  this  in- 
vestigation, and  especially  to  Mr.  Gustave  Fassin,  who  assisted 
materially  in  the  design  and  construction  of  the  apparatus  which 
was  employed. 


1  ADRIAN,  E.  D. :     "The  Basis  of  Sensation,"  W.  W.  Norton  &  Co.,  New  York, 

2  JACKSON,  EDWARD:    "Asthenopia,"  Amer.  J.  Ophth.,  4  (1921),  p.  218. 

3  LANCASTER,   W.    B.:     "Eye   Strain   and   Ocular   Discomfort  from   Faulty 
Illumination,"  Annals  of  Ophth.,  23  (1914),  p.  250.     "Ocular  Symptoms  of  Faulty 
Illumination,"  Amer.  J.  Ophth.,  15  (1932),  p.  783. 

4  JACKSON,  EDWARD:    "Visual  Fatigue,"  Amer.  J.  Ophth.,  4  (1921),  p.  119. 

5  LUCKIESH,  M.,  AND  Moss,  F.  K. :     "Seeing — A  Partnership  of  Lighting  and 
Vision,"  Williams  &  Wilkin  Co.,  Baltimore,  1931. 

6  Ives,  I.  E.:    "Studies  in  Illumination,"  U.  S.  Public  Health  Bulletin,  No.  181. 

7  HOWE,  LUCIEN:    "The  Measurement  of  Fatigue  of  the  Ocular  Muscles," 
Trans.  A.  M.  A.,  Sec.  on  Ophth.  (1912),  p.  423. 

8  LUEDDE,  W.  H.:    "The  Mechanism  of  Accommodation:    Facts  and  Fancies," 
Arch.  Ophth.,  7  (1932),  p.  40. 

9  BERENS,  CONRAD,  AND  STARK,  E.  K.:    "Studies  in  Ocular  Fatigue,"  Amer. 
J.  Ophth.,  15  (1932),  pp.  216,  527. 

10  COBB,  P.  W.:    "The  Influence  of  Pupillary  Diameter  on  Visual  Acuity," 
Amer.  J.  Physiol.,  36  (1915),  p.  335. 

11  MICHAELSON,  I.  C.:    "Angina  Capitis,"  Brit.  J.  Ophth.,  16  (1932),  p.  202. 

12  HEAD,  HENRY:     "On  Disturbances  of  Sensation  with  Especial  Reference  to 
'the  Pain  of  Visceral  Disease,"  Brain,  16  (1893),  p.  1;    Ibid.,  17  (1894),  p.  33; 
Ibid.,  19  (1896),  p.  153. 

13  REEVES,  P.:    "The  Response  of  the  Average  Pupil  to  Various  Intensities  of 
Light,"  /.  Opt.  Soc.  of  Amer.,  4  (1920),  p.  35. 

14  AREY,  LESLIE  B.:    "The  Function  of  the  Efferent  Fibres  of  the  Optic  Nerve 
of  Fishes,"  /.  Comp.  Neurol.,  26  (1916),  p.  213.     "The  Movements  in  the  Visual 
Cells  and  Retinal  Pigment  of  the  Lower  Vertebrates,"  J.  Comp.  Neurol.,  26 
(1916),  p.  121. 

15  LUCKIESH,  M.,  AND  Moss,  F.  K.:    "The  Rate  of  Visual  Work  on  Alternating 
Fields  of  Different  Brightnesses,"  /.  Frank.  Inst.,  200  (1925),  p.  731. 

16  GRANIT,  RAGNAR:    "Comparative  Studies  on  the  Peripheral  and  Central 
Retina,"  Amer.  J.  Physiol.,  94  (1930),  p.  41;    Ibid.,  95  (1930),  pp.  211,  229. 

390  PETER  A.  SNELL 

GRANIT,  RAGNAR,  AND  DAVIS,  W.  A.:  Ibid.,  98  (1931),  p.  644.  GRANIT,  RAGNAR, 
AND  HAMMOND,  E.  H.:  Ibid.,  98  (1931),  p.  654.  GRANIT,  RAGNAR,  AND  GRAHAM, 
C.  H.:  Ibid.,  98  (1931),  p.  664. 

17  PARSONS,    SIR   JOHN:     Bowman   Lecture,    "The   Foundations   of  Vision," 
Lancet,  2  (1925),  p.  123. 

18  GRANIT,  RAGNAR:    "The  Retina  as  a  Nervous  Center,"  Arch.  Ophth.  N.  S., 
6  (1931),  p.  104. 

19  ADRIAN,  E.  D.,  AND  MATTHEWS,  R.:    "The  Action  of  Light  on  the  Eye," 
J.  Physiol.,  63  (1927),  p.  378;  Ibid,  64  (1928),  p.  279;  Ibid.,  65  (1928),  p.  273. 

20  GRUNBAUM,  O.  F.  F.:    "On  Intermittent  Stimulation  of  the  Retina,"  /. 
Physiol.,  21  (1897),  p.  396. 

21  LYTHGOE,  R.  J.,  AND  TANSLEY,  K.:    "Regional  Variation  in  Sensitivity  to 
Flicker,"  Proc.  Royal  Soc.,  Series  B,  105  (1929),  p.  60. 



Summary. — The  author  discusses  various  defects  in  the  production  and  pro- 
jection of  motion  pictures,  upon  -which  the  occurrence  of  ocular  fatigue  is  assumed 
to  depend.  Remedies  for  these  defects  are  suggested  and  the  effect  upon  the  patronage 
of  a  theater  by  the  failure  to  apply  the  remedies  is  noted. 

Much  has  been  written  concerning  the  alleged  straining  of  eyes 
incident  to  the  viewing  of  motion  pictures.  Many  who  had  little 
knowledge  of  the  real  facts  of  the  matter  have  declared  such  strain 
to  be  severe;  they  have  succumbed  to  the  common  fallacy  of  basing 
their  conclusions  upon  inadequate  data,  and  have  failed  to  differ- 
entiate between  the  effects  of  viewing  motion  pictures  that  have 
been  properly  assembled  and  properly  projected,  and  of  viewing 
pictures  that  have  been  marred  by  avoidable  and  entirely  unnecessary 
defects,  which  shall  here  be  described. 

A  properly  assembled  picture,  properly  projected  in  a  properly 
illuminated  auditorium,  places  upon  the  eyes  a  burden  that  is  little 
if  any  greater  than  that  of  reading  ordinary  book  or  newspaper  print 
for  an  equal  length  of  time. 

However,  it  must  be  remembered  that  in  the  modern  motion  pic- 
ture theater  the  viewing  time  is  quite  long.  The  eyes  of  the  patrons 
are  used  continuously  for  the  entire  length  of  the  show;  and  on  that 
account  every  possible  effort  should  be  made  to  make  the  work  that 
the  eyes  have  to  do  as  easy  as  possible.  If  all  unnecessary  abuses 
and  eye  shocks  were  eliminated,  then  little  or  no  ocular  fatigue  would 

However,  it  must  be  admitted  that  the  matter  of  avoiding  eye- 
strain  has  been  very  lamentably  and  inexcusably  neglected.  It  is 
the  purpose  of  this  paper  to  point  out  the  nature  of  the  various 
defects  that  lead  to  ocular  fatigue  and  to  suggest  remedies  for  them. 

In  theaters,  the  chief  cause  of  eye  strain  that  lies  wholly  under  the 

*  Presented  at  the  Spring,  1933,  Meeting  at  New  York,  N.  Y. 
**  Motion  Picture  Herald,  New  York,  N.  Y. 


392  F.  H.  RICHARDSON  [j.  s.  M.  P.  E. 

control  of  the  projectionist  and  the  theater  manager  is  lack  of  defini- 
tion in  the  screen  image,  due  to  the  failure  of  the  projectionist  to 
focus  the  projection  lens  properly.  This  occurs  particularly  in 
theaters  in  which  the  projection  distance  is  quite  great,  as  it  is  then 
impossible  for  the  projectionist  to  determine  with  the  naked  eye 
whether  the  sharpness  of  focus  is  optimum  nor  not.  The  projec- 
tionist should  always  be  able  to  examine  the  screen  image  through 
a  high-power  double  glass,  held  rigidly  in  a  fixed  position  so  as  to  be 
always  available  for  instant  use. 

This  is  an  accessory  essential  to  good  work.  It  is  important  even 
in  theaters  in  which  the  projection  distance  is  short;  but  it  is  rarely, 
if  ever,  found  in  theaters.  Common  sense  should  tell  us  that  the 
projectionist  should  be  able  to  examine  the  screen  critically  and 
frequently.  He  can  not  examine  it  critically  with  the  naked  eye; 
and  he  is  further  handicapped  by  the  fact  that  in  modern  theaters 
the  observation  port  is  invariably  covered  with  glass,  usually  set  at 
an  angle  to  the  surface  of  the  screen. 

It  is  quite  true  that  a  few  theater  managers  provide  an  opera 
glass  of  greater  or  less  power.  However,  a  glass  that  is  not  fixed  in 
position  is  quite  inadequate;  usually  it  is  deposited  at  the  most 
convenient  point  by  the  man  who  used  it  last,  and  when  wanted 
must  be  sought  for.  As  a  consequence,  it  is  not  used  as  often  as  it 
ought  to  be.  Moreover,  the  screen  usually  is  examined  through 
the  glass  cover  of  the  port.  But  in  any  event,  a  glass  capable  of  being 
moved  is  of  little  value  because  the  projectionist  can  not  hold  it 
steadily  enough  in  his  hands  to  permit  him  to  examine  critically 
the  lines  on  a  distant  screen. 

Two  other  causes  of  poor  definition,  which  are  within  the  control 
of  theaters,  are  the  presence  of  oil  on  the  film,  which  is  a  matter  for 
theater  managers  to  take  up  with  exchanges,  as  well  as  to  make  sure 
that  oil  is  kept  from  the  films  while  in  the  theater ;  and  the  presence  of 
dirt  on  the  projection  lenses.  It  should  be  the  duty  of  the  pro- 
jectionist to  keep  the  lenses  perfectly  clean. 

The  next  cause  of  fatigue  of  the  eyes  to  be  considered  is  travel 
ghost,  either  in  sufficient  amount  to  be  obvious,  or  in  so  small  an 
amount  as  to  be  visible  only  by  observers  near  the  screen;  or,  even 
then,  visible  only  through  an  opera  glass.  Travel  ghost  is  seen  in  a 
surprisingly  large  number  of  theaters,  for  the  simple  reason  that  the 
projectionist  neglects  to  go  down  front,  at  least  once  a  week,  to  ex- 
amine the  screen  image  critically.  A  point  approximately  twenty- 

May,  1933]  AVOIDANCE  OF  EYE  FATIGUE  393 

five  feet  from  the  screen  is  the  best  position  from  which  to  examine 
the  image  when  using  an  opera  glass. 

Many  persons,  including  some  able  projectionists,  contend  that 
when  travel  ghost  is  so  faint  as  just  to  admit  of  detection,  it  can 
cause  no  harm.  This  is  a  wrong  conclusion.  Travel  ghost  in  any 
amount  tends  to  blur  the  horizontal  lines  of  the  screen  image,  pro- 
ducing upon  the  eyes  an  effect  similar  to  that  produced  by  a  slightly 
blurred  carbon  copy  of  typewritten  matter:  even  the  best  carbon 
copy  is  never  as  easy  to  read  as  the  original. 

Another  cause  of  eye-strain,  and  a  very  important  one,  may  be 
attributed  to  glare  spots,  the  evil  effects  of  which  are,  or  should  be, 
too  obvious  to  require  much  discussion.  The  theater  manager  who 
permits  a  glare  spot  to  exist  within  view  of  his  audience,  or  any 
portion  of  the  audience,  is  evidently  inconsiderate  of  his  own  interests, 
and  is  ignorant  of  the  seriousness  of  such  a  procedure.  By  way  of 
definition :  a  glare  spot  is  any  spot  of  white  light  of  greater  brilliancy 
than  the  general  illumination  of  the  auditorium  (other  than  the 
screen,  of  course),  in  the  field  of  view  of  the  patrons  looking 
at  the  screen.  A  white  frosted  electric  light  bulb,  white  frosted  light 
bowl,  or  an  indirect  lighting  fixture  located  within  the  field  of  vision 
as  one  views  the  screen  is  a  glare  spot,  and  may  be  highly  objection- 
able. A  spot  of  colored  light  may,  if  of  sufficient  brilliancy,  be  a  glare 
spot,  even  though,  perhaps,  a  less  serious  one. 

It  is  idle  to  assume  that  glare  spots  do  not  operate  to  decrease  box 
office  income.  If  after  the  show  the  patrons'  eyes  feel  uncomfortable, 
or  if  the  patrons  are  troubled  with  a  slight  headache  superinduced 
by  eye-strain,  they  are  not  as  likely  to  visit  the  theater  again  as 
soon  as  they  otherwise  might.  Although  the  patron  is  seldom  able 
to  place  the  blame  where  it  belongs,  he  attributes  his  fatigue  to  the 
picture,  not  knowing  or  realizing  that  it  was  not  the  screen  image  but 
a  spot  of  light — a  glare  spot — that  caused  his  discomfort. 

The  remedy  is  obvious:  eliminate  glare  spots.  Illuminating  the 
auditorium  exactly  as  for  a  show,  let  the  manager  view  the  screen 
from  various  parts  of  the  auditorium.  If  from  any  seat  a  white  light 
is  visible,  let  it  be  removed,  or  made  less  conspicuous.  If,  for  any 
reason  it  is  impracticable  to  eliminate  it  wholly,  by  extinguishing 
the  light,  let  the  portion  that  is  visible  to  the  audience  be  heavily 
tinted,  preferably  amber. 

Too  intense  illumination  of  the  screen  may  cause  eye-strain  for  one 
portion  of  the  audience;  or,  with  insufficient  illumination,  another 

394  F.  H.  RICHARDSON  [j.  s.  M.  p.  E. 

portion  of  the  audience  may  suffer  the  strain — a  condition  that  occurs 
in  theaters  in  which  the  viewing  distance  from  the  rear  is  very  great. 
In  such  auditoriums,  if  a  picture  of  reasonable  size,  which  can  be 
viewed  comfortably  from  the  front  seats,  be  projected,  intense 
illumination  of  the  screen  will  be  necessary  to  enable  those  seated 
at  the  rear  to  see  the  details  of  the  picture  with  comfort,  or  even  to 
distinguish  them.  However,  if  the  brilliancy  be  sufficient  for  those 
seated  at  the  rear,  it  will  be  too  intense  for  those  seated  at  the  front, 
and  may  cause  them  to  strain  their  eyes,  particularly  if  other  diffi- 
culties, which  will  now  be  discussed,  are  present. 

None  of  us  is  yet  able  to  say  with  confidence  just  what  the  in- 
tensity of  light  reflected  from  motion  picture  screens  should  be. 
That  is  a  question  that  involves  rather  grave  difficulties  and  many 
investigators  have  been  trying  to  answer  it  for  a  long  time.  The 
Projection  Practice  Committee  now  is  working  on  the  problem, 
with  hope  of  at  least  some  degree  of  success. 

The  chief  possible  causes  of  eye-strain  involved  in  viewing  motion 
pictures  that  are  more  or  less  under  the  control  of  the  theater  manager 
and  the  projectionist  have  been  discussed.  Attention  will  now  be 
directed  to  perhaps  the  worst  cause  of  all,  over  which  neither  pro- 
jectionist nor  manager  has  any  control  whatsoever.  That  it  exists 
is  indisputable ;  an.d  that  it  occurs  to  a  greater  or  less  extent  in  every 
picture  produced  must  be  admitted.  The  remedy  is  in  the  hands  of 
the  producers,  directors,  cinematographers,  and  film  editors. 

It  is  well  known  that  in  the  human  eye  the  quantity  of  light  ad- 
mitted to  the  retina  is,  within  limits,  automatically  controlled; 
and  that  the  adaptation  of  the  eye  to  changing  levels  of  illumination 
often  requires  an  appreciable  length  of  time.  Sudden  changes 
of  intensity  of  illumination,  occurring  faster  than  adaptation  proceeds, 
place  a  burden  on  the  seeing  process  that  may  lead  to  considerable 
ocular  fatigue.  The  greater  the  change  of  intensity,  the  longer  the 
time  required  for  complete  adaptation. 

It  is  evident,  therefore,  that  so  far  as  is  possible,  sudden  changes 
of  screen  illumination  should  be  avoided;  but  although  the  intensity 
of  the  projector  light  scource  and  the  optical  system  of  the  projector 
remain  unchanged,  the  quantity  of  light  that  reaches  the  screen 
varies  constantly,  often  instantaneously  and  in  extreme  amounts. 

Although  this  fact  is  very  apparent,  even  to  laymen,  it  has  been 
almost  utterly  disregarded  by  those  who  make  and  assemble  our 
motion  picture  productions;  who  seem  to  ignore  the  fact  that 

May,  1933]  AVOIDANCE  OF  EYE  FATIGUE  395 

instantaneous  transitions  from  the  dim  lighting  of  a  dense  scene  to 
the  full  glare  of  an  almost  white  screen  is  objectionable.  Every 
production  provides  one  or  several  examples  of  such  a  transition. 

Assume  a  dense  interior  scene,  in  which  appear  two  persons,  one 
of  whom  hands  to  the  other  a  letter  to  read;  instantly  the  illumina- 
tion of  the  screen  changes  from  a  very  low  intensity  to  that  of  prac- 
tically the  blank  screen.  It  needs  no  argument  to  prove  that  such  a 
sudden  change  causes  a  "shock"  to  the  eyes  of  all  those  viewing 
the  screen.  In  order  to  avoid  such  a  state  of  affairs,  the  letter  or 
message  could  be  shown  as  in  white  letters  on  a  dark  gray  back- 
ground, or  as  black  letters  on  a  lighter  shade  of  gray.  The  shock 
would  thus  be  very  materially  reduced,  and  the  message  be  made 
not  only  as  legible,  but  more  so,  because  until  the  eye  recovers  from 
the  shock  and  adjusts  itself  to  the  new  level  of  illumination,  its 
ability  to  read  the  message  without  straining  itself  to  do  so  will  be 
much  less  than  normal. 

"But,"  the  producer  will  protest,  "it  would  be  unnatural  to  show 
a  letter  on  other  than  white  paper,  written  with  other  than  black 

Quite  true;  however,  producers  often  do  incorporate  things  not 
exactly  natural  in  their  productions.  For  example,  how  often  have 
we  seen  the  feminine  "star"  made  up  and  beautifully  attired,  emerge 
from  the  water  into  which  the  plot  had  driven  her,  with  her  attire 
in  perfect  order — an  effect  that  is  admittedly  unnatural.  In  order 
to  conform  to  the  nature  of  things,  the  "star"  would  have  to  emerge 
from  the  water  in  a  damp  and  bedraggled  condition. 

Such  letters  and  written  messages  constitute  only  one,  though 
usually  the  worst  cause  of  abuse  of  the  eyes  of  theater  patrons. 
How  often  do  we  see  dense  scenes  followed  by  scenes  that  are  much 
less  dense.  For  example,  an  interior,  or  a  scene  in  the  woods,  followed 
by  a  marine  view  shown  brilliantly  on  the  screen.  The  change  from 
a  brilliant  scene  to  a  dense  one  causes  little  if  any  harm ;  but  a  change 
in  the  opposite  sense  does.  The  difficulty  could  be  avoided  with  rela- 
tively little  additional  trouble  on  the  part  of  the  directors  and  cine- 
matographers.  The  instructions  are :  "At  the  beginning  of  a  brilliant 
scene  which  is  to  follow  a  dense  one,  let  the  scene  be  underexposed 
and  gradually  brought  up  to  normal."  Certainly  such  a  procedure 
would  provide  an  interval  of  time  during  which  the  eye  could  adjust 
itself  to  the  change  of  illumination  without  noticeable  strain. 



Summary. — An  illustrated  description  is  given  of  new  sound  recording  equipment 
having  an  extended  frequency  range1  and  capable  of  making  recordings  and  re- 
recordings  on  either  35-  or  16-mm.  film.  Contact  prints  made  from  the  35-mm. 
recordings  or  re-recordings,  when  played  on  a  reproducing  equipment  having  a 
flat  response  characteristic,  produce  sound  outputs  that  do  not  vary  more  than  plus 
or  minus  two  decibels  over  the  frequency  range  50  to  9000  cycles.  The  equipment 
is  composed  of  units  that  are  light  in  weight,  are  small  and  compact  but  rugged, 
consume  little  power  and  are  easily  installed  and  operated  for  either  studio  or  portable 

Some  of  the  features  of  the  equipment  are  (a)  symmetrical  variable  width  recording 
with  improved  ground  noise  reduction;  (&)  a  new  large  mirror  galvanometer;  (c) 
permanent  magnet  ribbon  microphones  operated  remotely  from  their  amplifiers; 

(d)  improved  constant  impedance  mixer  using  variable  bridged  "T"  type  attenuators; 

(e)  correction  for  the  response  of  the  human  ear  to  speech  reproduced  at  greater  than 
normal  volume;    (/)  new  amplifying  equipment  providing  improved  quality  and 
quieter  operation;   and  (g)  new  high-quality  film  phonograph  and  recorders. 

With  previous  types  of  recording  equipment,  about  6000  cycles 
was  the  upper  limit  of  uniform  output  when  measured  on  a  uniform- 
response  reproducing  equipment.  Even  at  that  frequency,  con- 
siderable compensation  was  required  to  counterbalance  the  losses 
in  the  system,  including  processing  losses.  The  frequency  response 
was  subject  to  considerable  variation  due  to  the  mechanical  resonance 
of  the  recording  galvanometer  or  vibrator,  the  cavity  resonance  of 
the  condenser  microphone,  and  the  location  of  the  microphone 
in  the  sound  field.  The  height  of  the  mechanical  resonance  peak  of 
the  galvanometer  was  very  difficult  to  maintain  constant,  due  to  the 
change  of  damping  with  the  temperature,  age,  etc.  The  frequency 
characteristic  of  the  condenser  microphone  varied  considerably, 
depending  upon  the  angle  of  incidence  of  the  sound  waves.  With 
these  variations,  it  was  very  difficult  to  maintain  good  response 

*  Presented  at  the  Spring,  1933,  Meeting  at  New  York,  N.  Y. 
**  Engineering  Department,  RCA  Victor  Co.,  Camden,  N.  J. 


even  up  to  6000  cycles.  The  problem  became  more  involved  when 
re-recordings  were  made,  especially  when  it  was  desired  to  combine 
or  mix  the  outputs  of  one  or  more  microphones  with  that  of  a  film 
phonograph.  It  was  necessary  to  compensate  either  for  the  micro- 
phones or  for  the  film  phonograph  in  order  to  obtain  similar  fre- 
quency characteristics;  at  the  same  time,  it  was  necessary  to  main- 
tain the  correct  over-all  compensation.  Due  to  these  difficulties, 
the  degree  of  compensation  and  the  methods  of  obtaining  it  varied 
greatly  from  one  equipment  to  another;  and,  in  the  case  of  re- 
recording,  varied  between  different  films.  In  any  case,  it  was  usually 
left  to  the  discretion  of  the  recordist. 

Recent  improvements  in  the  quality  of  sound  reproducing  equip- 
ment have  furnished  an  added  incentive  to  improve  the  quality  of 
sound  recordings.  It  is  always  desirable  that  the  quality  of  sound 
recordings  be  superior  to  that  of  the  reproducing  equipment,  because 
sound  from  old  recordings  often  is  "dubbed"  or  re-recorded  into 
current  productions. 

The  film  phonographs  usually  consisted  of  slightly  revised  standard 
reproducing  sound-heads.  This  type  of  unit  did  not  provide  the 
same  constancy  of  film  speed  as  the  recorder  did,  and  thereby  caused 
unnecessary  distortion.  Furthermore,  these  units  abraded  the  film 

The  unusually  rapid  increase  in  popularity  of  16-mm.  sound-film 
recordings,  both  in  industry  and  in  the  home,  has  provided  a  new 
field  for  recording,  which,  though  new,  is  closely  related  to  35-mm. 
recording.  It  is  to  be  expected  that  a  large  part  of  the  16-mm. 
sound  film  will  be  re-recorded  from  the  master  positive  or  from 
prints  of  standard  35-mm.  sound  recordings,  as  this  provides  a 
very  economical  means  of  obtaining  good  quality  16-mm.  sound 

It  is  the  purpose  of  this  paper  to  describe  a  sound  recording  equip- 
ment that  was  designed  for  practical  operation,  keeping  in  mind 
these  considerations  as  well  as  others  advanced  by  a  number  of 
studios  using  previous  types  of  equipment.  Some  of  the  advantages 
of  this  equipment  are  as  follows: 

Recordings  or  re-recordings,  or  combined  recordings  and  original 
recordings  may  be  made  without  altering  the  high-frequency  com- 
pensation. The  output  from  a  contact  print  of  the  recorded  film, 
when  played  on  high  fidelity  reproducing  equipment,  is  a  faithful 
reproduction,  within  plus  or  minus  two  decibels  over  the  frequency 

398  SIDNEY  READ,  JR.  [j.  s.  M.  P.  E. 

range  50  to  9000  cycles,  of  the  original  sound  or  of  the  output  of  the 
film  from  which  the  re-recording  is  made. 

The  operation  of  the  equipment  is  greatly  simplified.  Consider- 
able simplification  in  operation  results  from  compensating  entirely 
in  one  unit,  which  is  common  for  recording  and  re-recording,  the 
response  of  all  the  remaining  units  being  essentially  constant  over 
the  frequency  range  that  it  is  desired  to  cover.  This  makes  it 
possible  to  record  or  re-record  without  the  usual  difficulty  of  varying 
the  compensation.  The  compensator  panel,  the  unit  that  provides 
the  necessary  correction  for  losses  sustained  in  processing,  has  only 
three  degrees  of  compensation:  namely,  (1)  for  35-mm.  recording 
or  re-recording;  (2)  for  16-mm.  recording  or  re-recording;  and  (3) 
uniform  response  to  provide  for  testing.  A  three-position  switch, 
suitably  designated,  is  provided  for  selecting  the  degree  of  com- 

Compensation  is  provided  to  correct  for  the  change  in  frequency 
response  of  the  ear  with  an  increase  in  sound  intensity.  As  speech 
is  nearly  always  reproduced  at  levels  higher  than  the  original,  this 
compensation  consists  in  attenuating  both  the  low  and  the  extremely 
high  frequencies.  Thus  the  recorded  speech  may  be  amplified  to 
the  level  required  in  the  theater  without  changing  its  quality.  A 
switch  on  the  microphone  mixing  panel  provides  for  controlling  the 
attenuation  while  speech  is  being  recorded.  This  compensation  is 
entirely  independent  of  the  compensation  for  processing  losses  pre- 
viously referred  to.  The  latter  is  required  for  recording  all  sounds, 
while  both  are  required  only  when  recording  speech  or  other  low 
level  sounds. 

Flexibility  is  improved,  as  regards  the  location  of  the  units  relative 
to  one  another.  This  is  accomplished  by  making  the  impedance  of 
the  coupling  lines  between  all  units  of  such  a  value  as  to  permit  an 
appreciable  distance  between  the  units  with  a  negligible  change  in 
frequency  characteristic. 

All  the  amplifying  and  control  units,  with  the  exception  of  the 
microphone  and  phototube  amplifiers,  are  designed  for  mounting  on 
a  standard  relay  rack  or  for  portable  use  with  interconnecting  cables 
between  the  different  units.  Also,  the  controls  are  so  located  as  to 
facilitate  this  kind  of  operation.  This  is  quite  desirable  because  in 
some  applications  it  may  be  convenient  to  locate  the  mixer  as  well 
as  the  complete  amplifying  and  recording  equipment  in  one  room; 
whereas,  in  other  applications,  it  may  be  desirable  to  operate  the 

May,  1933] 



mixer  and  monitoring  system  remotely  from  the  other  amplifying 
equipment;  and  operate  this  amplifying  equipment,  in  turn,  re- 
motely from  the  recorder  or  re-recorder.  A  relatively  small  amount 
of  power  is  required  to  operate  this  equipment. 

A  high-quality  film  phonograph  is  provided.  This  unit  is  greatly 
improved  as  to  frequency  characteristic  and  speed  variation,  and, 
in  addition,  abrades  the  film  considerably  less. 

Fig.   1  shows  a  photograph  of  an  installation  at  the  studios  of 

FIG.  1. 

High  fidelity  film  recording  system  installed  at  the  Burton  Holmes 
Studio,  Chicago,  111. 

Burton  Holmes  Lectures,  Inc.,  at  Chicago,  111.  From  left  to  right 
are  shown  a  35-mm.  recorder,  amplifier  and  control  rack,  phototube 
amplifier,  and  a  35-  to  16-mm.  re-recorder  (consisting  of  a  35-mm. 
film  phonograph  and  a  16-mm.  recorder  mounted  on  the  same  base 
and  mechanically  connected). 

Fig.  2  shows  a  diagram  of  the  new  recording  equipment.  Four 
microphones,  type  44- A,  are  connected  to  their  respective  micro- 
phone amplifiers,  type  PA-82.  The  impedance  of  each  line  between 



[J.  S.  M.  P.  E. 

the  microphone  and  the  microphone  amplifier  is  250  ohms.  One  or 
more  of  the  microphones  and  microphone  amplifiers  may  be  replaced 
by  phototubes  and  phototube  amplifiers,  type  PA-79,  when  it  is  de- 
sired to  re-record.  The  phototube  is  located  in  the  film  phonograph, 
and  is  connected  to  the  phototube  amplifier  by  a  50,000-ohm  line. 
This  line  is  about  two  and  one-half  feet  long,  and  consists  of  a  low- 
capacity  cable  well  shielded  against  external  fields.  The  lines  be- 
tween the  outputs  of  the  microphone  and  phototube  amplifiers  and 
the  input  of  the  microphone  mixing  panel  have  an  impedance  of 








:R  s 



















FIG.  2.     Sound  recording  equipment;  diagram  of 
components  and  interconnecting  cables. 

250  ohms.  These  outputs  are  combined  in  a  microphone  mixer, 
type  PB-37,  in  which  it  is  possible  to  adjust  independently  the 
volume  output  of  each  microphone  or  phototube  amplifier,  as  well 
as  that  of  the  combined  output.  The  microphone  distribution 
panel,  type  PB-12,  serves  as  a  junction  box  for  connecting  the  outputs 
of  the  microphone  and  phototube  amplifiers  to  the  inputs  of  the 
microphone  mixer  and  for  furnishing  the  d-c.  power  for  those  units. 
The  output  of  the  microphone  mixer  is  fed  through  a  500-ohm  line 
into  the  compensator  panel,  type  PB-70.  This  unit  accentuates 


the  high  frequencies  so  as  to  correct  for  the  processing  losses  at  those 
frequencies.  The  output  of  the  compensator  panel  is  connected  to 
the  input  of  the  type  PA -7 5  recording  amplifier  through  a  500-ohm 
line.  This  amplifier  raises  the  audio  voltage  to  a  sufficiently  high 
level  to  operate  the  recording  galvanometers.  The  connection  is 
made  by  means  of  a  500-ohm  line.  A  small  part  of  the  energy  fed 
to  the  recorder  is  utilized  in  operating  the  ground  noise  reduction 
amplifier,  type  PA -71.  This  amplifier  rectifies  and  filters  the  audio 
voltage  and  furnishes  a  biasing  current  for  the  auxiliary  or  bias 
winding  of  the  recording  galvanometer.  The  input  of  the  monitoring 
amplifier,  type  PA-76,  is  connected  in  parallel  with  the  output  of 
the  recording  amplifier,  the  connection  being  made  through  terminals 
on  the  decompensator,  which  is  physically  a  part  of  the  type  PB-70 
compensator  panel.  The  monitoring  amplifier  has  a  high-impedance 
input,  thus  requiring  a  negligible  amount  of  audio  power  from  the 
recording  amplifier.  The  decompensator  provides  sufficient  high- 
frequency  attenuation  to  correct  for  the  increase  of  voltage  with 
frequency,  caused  by  inserting  a  portion  of  the  compensator  into 
the  input  of  the  recording  amplifier,  as  well  as  that  resulting  from 
the  increase  of  galvanometer  impedance  with  frequency. 

Fig.  2  also  shows  the  power  connections  to  the  various  units. 
The  power  for  the  filaments  in  the  microphone  distribution  panel  is 
obtained  from  an  8- volt  storage  battery,  requiring  2.5  amperes  when 
four  microphone  or  phototube  amplifiers  are  used.  The  plate 
voltage  is  180,  supplied  by  medium  duty  "B"  batteries  delivering 
28  milliamperes  when  four  microphone  amplifiers  are  used  and  14 
milliamperes  when  four  phototube  amplifiers  are  used.  The  same 
"A"  supply  may  be  used  in  common  for  this  unit,  the  booster  ampli- 
fier (single  stage  of  amplification  in  the  type  PB-70  compensator 
panel),  the  recording  amplifier,  and  the  ground  noise  reduction 
amplifier.  However,  it  is  usually  desirable  that  the  "B"  voltage 
for  this  unit  be  obtained  from  a  separate  battery.  The  filament 
current  for  the  booster  amplifier  of  the  compensator,  the  recording 
amplifier,  and  the  ground  noise  reduction  amplifier  is  obtained  from 
a  common  8-volt  storage  battery.  These  units  require  a  total  cur- 
rent of  6  amperes.  The  plate  voltage  for  the  booster  amplifier  of 
the  compensator  and  the  recording  amplifier,  180  volts,  is  obtained 
from  heavy  duty  dry  "B"  batteries.  The  total  current  is  60  milli- 
amperes. The  plate  voltage  for  the  ground  noise  reduction  amplifier, 
90  volts,  is  obtained  from  heavy  duty  dry  "B"  batteries,  delivering 



[J.  S.  M.  P.  E, 

a  total  current  of  45  milliamperes.  The  monitoring  amplifier  requires 
a  total  power  of  70  watts  from  a  1 10-volt,  50-  to  60-cycle  source.  The 
field  of  the  monitoring  loud  speaker  is  excited  by  the  monitoring 
amplifier.  The  power  for  the  fields  and  exciter  lamps  of  the  re- 
corders and  film  phonographs  is  supplied  by  a  storage  battery.  An 
8-volt  battery  is  sufficient  except  when  a  film  phonograph  is  used, 
in  which  case  a  12-volt  battery  is  required.  The  total  current  for 
each  recorder  is  7.6  amperes,  while  that  for  a  film  phonograph  is 
6.6  amperes.  The  power  for  driving  the  motors  of  the  recorders 
and  film  phonographs  is  obtained  from  a  3-phase  a-c.  source  or  from 
a  master  selsyn  generator.  These  units  may  be  obtained  for  either 
50-  or  60-cycle  as  well  as  for  selsyn  operation. 

FIG.  3. 

Sound  recording  equipment;   frequency  characteristic  of 
recorded  amplitude. 

A  standard  35-mm.  recording  equipment,  type  PM-29,  as  shown 
in  Fig.  2,  weighs  approximately  500  pounds,  including  one  35-mm. 
recorder,  four  velocity  microphones,  four  microphone  amplifiers, 
four  1000-ft.  film  magazines,  and  all  bias  batteries.  Fifty  pounds 
is  the  maximum  weight  of  any  unit,  except  the  recorder,  which  weighs 
approximately  185  pounds.  The  total  weight  of  the  recommended 
plate  supply  batteries  is  approximately  125  pounds.  If  the  amplify- 
ing equipment  is  mounted  on  a  standard  rack,  type  9-D,  the  weight 
of  the  equipment  will  be  increased  approximately  75  pounds. 

May,  1933] 



Fig.  3  shows  the  over-all  frequency  characteristic,  measured  from 
the  input  of  one  of  the  fhixers  to  the  recorded  amplitude  on  the  film, 
for  both  35-  and  16-mm.  recording  or  re-recording.  The  increase 
of  response  at  the  high  frequencies  counteracts  the  film  loss  so  as 
to  make  the  output  from  a  print  of  the  recorded  film  essentially 
constant.  Of  course,  in  order  to  obtain  such  a  result,  it  is  necessary 
that  the  sound  reproducing  equipment  have  an  over-all  frequency 
characteristic  that  is  flat  considering  the  width  of  the  slit  and  the 
gas  amplification  of  the  phototube. 

Fig.  4  shows  the  measured  characteristic  of  a  35-mm.  print  made 
from  a  35-mm.  negative,  which,  in  turn,  was  recorded  on  a  pro- 
duction recording  equipment,  maintaining  constant  the  input  voltage 
to  one  of  the  inputs  of  the  microphone  mixer.  Since  the  frequency 
characteristic  of  the  ribbon  microphone  and  its  amplifier  and  that 

FIG.  4.     Sound  recording  equipment;  frequency  characteristic  of  35-mm. 
recorded  film  after  printing. 

of  the  phototube  amplifier  including  the  film  phonograph  slit  loss 
are  essentially  flat,  as  will  be  shown  later,  it  is  easily  seen  from  this 
curve  how  faithfully  the  output  from  prints  of  recorded  and  re- 
recorded films  will  approach  the  sound  input  to  the  microphone  and 
the  output  from  the  film  played  in  the  film  phonograph.  This 
output  is  a  faithful  reproduction,  within  plus  or  minus  2  decibels, 
of  the  original  sound  for  frequencies  between  50  and  9000  cycles 
per  second. 


The  following  units  are  available  and  may  be  used  with  the  same 
type  of  amplifying  equipment:  (1)  type  PR-18,  35-mm.  recorder; 
(2)  type  PR-19,  16-mm.  recorder;  (3)  type  PB-36,  35-mm.  film 
phonograph;  (4)  type  PB-38,  35-  to  16-mm.  re-recorder. 



[J.  S.  M.  P.  E. 

Since  a  paper2  giving  a  detailed  description  of  these  units  has 
already  been  published,  only  the  parts  involved  in  the  audio  circuits 
will  be  considered. 

Fig.  5  is  a  schematic  diagram  of  the  audio  and  power  circuits  of 
a  35-mm.  recorder.  From  this  diagram,  it  may  be  seen  that  the 
audio  signal,  on  entering  the  recorder,  passes  into  an  impedance  of 
500  ohms  and  is  stepped  down  to  match  the  2-ohm  modulation 
coil  of  the  galvanometer.  The  drop  in  voltage  across  the  25-ohm 
resistor,  in  series  with  the  500-ohm  side  of  the  transformer,  furnishes 
the  necessary  voltage  for  operating  the*  ground  noise  reduction 
amplifier.  The  auxiliary,  or  bias  winding  of  the  galvanometer, 

-»-JQ  TYPE  PA-75 



J!tTO  TYPE  PA- 11 
*_-[_».e<NR.  AMPLIFIER 


T0  3Mf-  fc°  rd- 
-          220  VOLT 
--»•     SUPPLY 

FIG.  5.     Schematic  diagram  of  model  4PR18A1  35-mm.  film  recorder. 

receives  the  proper  amount  of  direct  current  to  reduce  the  clear 
portion  of  sound  track  when  no  audio  signal  is  applied,  and  to  increase 
the  clear  portion  sufficiently  so  as  to  prevent  overshooting  when 
modulation  occurs.  A  more  detailed  description  of  this  action  will 
be  given  when  describing  the  ground  noise  reduction  amplifier. 
A  switch  in  the  audio  circuit  of  the  recorder  provides  for  disconnect- 
ing the  audio  output  of  the  recording  amplifier  from  the  modulation 
winding  and  also  from  the  input  of  the  ground  noise  reduction  ampli- 
fier to  allow  for  monitoring  without  the  galvanometer  in  the  circuit 
and  for  protecting  the  galvanometer  when  not  in  use.  The  galvanome- 


ter  furnished  with  this  unit  is  of  the  electromagnetic  type,  and  is 
more  sensitive  than  the  string  or  oscillograph  type  of  unit,  making 
it  possible  to  use  a  larger  mirror.  The  increased  size  of  mirror 
reduces  the  stray  light  and  allows  a  greater  depth  of  focus  of  the  slit 
on  the  film,  thereby  resulting  in  a  greater  response  at  the  high  fre- 
quencies. The  deflection  of  this  unit  is  substantially  constant  for 
all  frequencies  below  the  resonant  frequency,  which  is  9000  cycles. 
The  damping  is  such  as  to  limit  the  deflection  at  resonance  to  about 
three  decibels  above  the  deflection  at  1000  cycles. 

The  audio  and  power  circuits  of  the  16-mm.  recorder  are  identical 
to  those  of  the  35-mm.  unit,  except  in  that  a  low-pass  filter  is  in- 
serted in  the  500-ohm  input  circuit  in  order  to  suppress  all  frequencies 
greater  than  4000  cycles.  The  reproduction,  from  16-mm.  film, 
of  frequencies  greater  than  that  results  in  considerable  distortion 
and  very  little  useful  output,  because  of  the  reduced  speed  of  the 
film,  thirty-six  feet  per  minute. 

The  35-mm.  film  phonograph  is  somewhat  similar  to  the  35-mm. 
recorder.  The  recording  optical  system  is  replaced  by  a  reproducing 
optical  system,  and  the  phototube  is  so  mounted  that  light  from  the 
optical  system  passes  through  the  sound  track  and  thence  to  the 
light-sensitive  element. 

The  35-  to  16-mm.  re-recorder  consists  of  a  35-mm.  film  phonograph 
and  a  16-mm.  recorder  mounted  on  the  same  base  and  mechanically 
connected.  This  arrangement  provides  a  simple  means  for  re- 
recording  from  35-  to  16-mm.  film  without  the  usual  selsyn  installa- 


The  velocity  microphone3   provides  for: 

(1)  A  transformation  of  sound  into  electrical  energy  that  is  practically  uni- 
form at  frequencies  from  70  to  10,000  cycles  per  second. 

(2)  A  permanent  magnet  type  of  field. 

(3)  A  uniform  directional  characteristic  for  all  frequencies. 

(4)  Remote  operation  as  regards  the  microphone  amplifier. 

(5)  An  open  circuit  voltage  output  of  90  microvolts  per  dyne  per  sq.  cm., 
referred  to  an  output  impedance  of  250  ohms. 

(6)  Cushion  and  suspension  mounting,  with  provision  for  rotation  about  both 
vertical  and  horizontal  axes. 

(7)  Protection  against  disturbances  due  to  wind. 

Fig.  6  shows  two  views  of  the  44-A  velocity  microphone,  with  and 



[J.  S.  M.  P.  E. 

without  a  wind  screen.  This  wind  screen  can  be  easily  attached  to 
or  removed  from  the  microphone ;  it  is  not  required  for  studio  work, 
because  suitable  protection  against  wind  disturbance  which  would 




The  velocity  microphone  (44- A)  showing  suspension  mounting  and 
wind  screen. 


R1&50N        X 


FIG.  7.     Velocity  microphone  (44- A}  with  ou 
screen  removed. 

half  of  inner  cover 

be  encountered  in  this  kind  of  work,  as  well  as  protection  against 
damaging  the  ribbon,  is  provided  by  two  cover  screens. 

Fig.  7  is  a  view  of  the  microphone  with  the  outer  and  one-half 


the  inner  cover  screen  removed.  Fundamentally,  this  microphone 
consists  of  a  thin  aluminum  ribbon  suspended  in  a  magnetic  field 
produced  by  permanent  magnets.  The  sound  waves  cause  this 
ribbon  to  vibrate  in  the  magnetic  field,  thereby  producing  a  voltage 
drop  between  the  ends  of  the  ribbon.  A  transformer  is  used  for 
stepping  up  this  voltage  sufficiently  to  operate  into  the  250-ohm 
input  of  the  microphone  amplifier. 

One  advantage  of  the  velocity  microphone  is  its  ability  to  operate 
uniformly,  independently  of  changes  in  climatic  conditions,  such  as 
atmospheric  pressure,  humidity,  and  temperature,  any  or  all  of  which 
considerably  affect  other  microphones. 

Another  important  advantage  of  the  velocity  microphone  is  its 
directional  property.  Since  the  ribbon  is  suspended  in  free  space, 
sound  waves  approaching  the  microphone  in  the  plane  of  the  ribbon 
have  no  effect  upon  it.  Sound  waves  impinging  on  either  side  of  the 
ribbon  and  perpendicularly  incident  to  the  plane  of  the  ribbon  have 
a  maximum  effect.  For  equal  distances  from  the  transmitter,  sound 
waves  incident  at  an  angle  of  70  or  80  degrees  from  the  normal  to 
the  ribbon  will  have  practically  no  effect ;  whereas,  for  those  incident 
at  an  angle  of  45  degrees  from  the  perpendicular,  the  sensitivity  is 
approximately  70  per  cent  of  the  maximum,  and  the  quality  is  un- 
changed. The  response  of  this  microphone  to  sounds  originating 
in  random  directions  is  one-third  that  of  a  non-directional  micro- 
phone. For  the  same  allowable  recorded  reverberation,  the  velocity 
microphone  can  be  used  at  a  distance  1.7  times  the  distance  at  which 
a  non-directional  microphone  can  be  used.  It  is  at  once  apparent 
that  this  characteristic  is  of  great  value  in  overcoming  some  of  the 
difficulties  encountered  in  reverberant  sets  by  reducing  the  response 
to  undesired  reflected  sounds,  and  in  obtaining  better  balance  and 
selectivity  in  recording.  Extraneous  direct  or  reflected  sounds 
approaching  the  microphone  from  the  side  will  have  little  or  no 
effect.  The  background  noises  and  reflected  sounds  are  therefore 
reduced;  an  effect  that  increases,  by  comparison,  the  quality  of 
the  direct  sounds,  and  reduces  the  necessity  of  using  highly  sound- 
proofed booths  and  "blimps,"  provided  that  advantage  be  taken  of 
the  directional  characteristic  when  placing  the  cameras.  The 
camera,  for  example,  may  be  operated  outside  the  booth  if  it  be 
placed  in  the  "dead  zone;"  that  is,  in  the  plane  of  the  ribbon  of  the 
microphone,  provided  that  none  of  the  camera  sound  is  returned 
to  the  microphone  from  any  other  direction  by  reflecting  surfaces. 



[J.  S.  M.  P.  E. 

This  condition  may  generally  be  realized  in  out-of-door  recording, 
and  in  the  studio  a  considerable  reduction  in  the  amount  of  noise 
picked  up  from  the  camera  may  be  effected. 

This  type  of  microphone  responds  faithfully  to  all  sound  vibrations 
over  the  range  of  frequencies  from  70  to  10,000  cycles.  Curve  1 
of  Fig.  8  represents  the  free-wave  calibration  of  this  microphone, 
showing  that  the  output  at  10,000  cycles  is  only  3.5  decibels  below 
that  at  1000  cycles.  No  "peaks"  or  "dips"  occur  in  the  character- 
istic of  this  microphone  that  deviate  from  curve  2  by  more  than  1 
decibel,  which  represents  approximately  the  degree  of  dependence 
that  may  be  placed  upon  the  acoustical  measurements.  This 
is  a  matter  of  prime  importance  in  choosing  a  microphone,  as  sharp 
"peaks"  or  "dips"  in  the  characteristic  cause  very  objectionable 


FIG.  8.     Sound  recording  equipment;   frequency  characteristic  of  velocity 
microphone  (44- A)  and  microphone  amplifier  (PA-82). 

distortion,  especially  when  a  wide  frequency  range  is  covered.  The 
uniformity  of  the  response  is  due  principally  to  the  smallness  of  the 
size  and  mass  of  the  velocity  element  placed  in  free  space.  Other 
microphones  are  prevented  from  producing  as  faithful  a  response 
by  the  size  or  mass  of  their  diaphragms,  or  by  the  fact  that  the 
diaphragms  are  required  to  work  against  more  or  less  closed  air 
chambers.  The  faithfulness  of  response  of  this  microphone  imparts 
a  naturalness  of  tone  and  a  distinctness  of  speech  not  hitherto  attain- 
able with  other  units. 

The  open  circuit  voltage  of  the  microphone  is  90  microvolts  for  a 
sound  input  of  1  dyne  per  sq.  cm.  The  output  impedance  of  the 
unit  is  250  ohms.  This  sensitivity  is  approximately  2x/2  times  that 
of  the  condenser  microphones  generally  used. 

May,  1933] 




The  microphone  amplifier  provides  for: 

(1)  Sufficient  amplification  (50  decibels)  to  increase  the  voltage  output  of 
the  velocity  microphone  to  a  suitable  level  for  mixing. 

(2)  Slight  accentuation  of  the  high  frequencies,  so  as  to  compensate  for  the 
reduction  that  occurs  at  those  frequencies  in  the  velocity  microphone;    thereby 
resulting  in  a  uniform  response  up  to  10,000  cycles. 

(3)  Negligible  generation  of  noise. 

Fig.  9  is  a  side  view  of  the  PA-82  microphone  amplifier  with  the 
cover  removed  and  the  radiotrons  in  position.     As  the  photograph 

CCA- 23fo 

TYPE    P 







FIG.  9.     Microphone  amplifier  (PA -82};   cover  removed. 

shows,  the  radiotrons  and  amplifier  assembly  are  mounted  on 
cushions  on  two  studs,  which  later  are  mounted  on  the  base  and 
act  as  a  supporting  structure  for  the  case  of  the  amplifier.  The 
projecting  portion  of  the  studs  is  threaded  for  thumb  nuts,  which 
hold  the  cylindrical  cover  in  place.  Ears  are  provided  on  the  cover 
for  suspending  the  unit.  The  input  connection  from  the  microphone 
to  the  unit  is  made  by  a  cannon  type  P  receptacle,  while  the  output 
and  power  supply  connections  are  made  to  the  microphone  dis- 
tribution panel  by  means  of  a  cannon  type  F  plug.  As  shown  by  the 
schematic  diagram,  Fig.  10,  the  microphone  amplifier  consists  of  an 



[J.  S.  M.  P.  E. 

input  transformer  feeding  an  R.CA-236  radiotron  resistance-coupled 
to  an  RCA-237  radiotron  which  is,  in  turn,  coupled  to  a  250-ohm 
line  by  means  of  a  step-down  transformer.  The  bias  voltage  for 
the  first  stage,  including  the  screen  grid,  is  obtained  from  a  "bleeder," 
while  the  second  stage  is  self -biased.  The  plate  and  screen  grid 
circuits  are  individually  filtered  so  as  to  prevent  disturbances  from 
the  power  supply  from  entering  the  audio  circuit.  By  using  radio- 
trons  of  the  heater  type,  such  disturbances  are  avoided  in  the  fila- 
ment circuit.  The  bias  resistor  of  the  second  stage  is  by-passed  by 
a  small  capacitor,  which  provides  sufficient  high-frequency  com- 
pensation to  counteract  the  slight  loss  of  high  frequencies  in  the 

The  combined  frequency  characteristic  of   the  44-a  microphone 
and  the  microphone  amplifier  is  shown  by  curve  2  of  Fig.  8,  which 


0      OUTPUT 

FIG.  10.     Schematic  diagram  of  microphone  amplifier  (PA-82). 

does  not  deviate  from  a  straight  line  by  more  than  ±1  decibel, 
from  150  to  10,000  cycles.  The  response  decreases  slightly  from 
150  to  70  cycles,  the  response  at  the  latter  frequency  being  2.4 
decibels  below  that  at  1000  cycles. 

The  noise  generated  in  the  amplifier,  due  to  "shot  effect"  in  the 
radiotrons  and  to  other  causes,  has  been  reduced  to  a  negligible 
value;  in  fact,  such  noise  represents  only  about  10  per  cent  of  the 
total  noise  that  would  be  encountered  due  to  the  thermal  agita- 
tion, at  room  temperature,  of  a  high-grade  250-ohm  wire-wound 
resistor  connected  across  the  input  terminals.  The  plate  supply 
required  for  this  amplifier  is  180  volts  at  a  current  of  7  milliamperes. 
The  required  filament  supply  is  8  volts  at  0.6  amperes. 




The  phototube  amplifier  provides  for: 

(1)  Sufficient  amplification  (27  decibels)  to  increase  the  output  voltage  of  the 
phototube  to  a  suitable  level  for  mixing  with  the  outputs  of  the  microphone 

(2)  Slight  accentuation  of  the  high  frequencies,  so  as  to  compensate  for  the 
insufficient  response  of  the  phototube  at  those  frequencies,  as  well  as  for  the  losses 
due  to  the  width  of  the  scanning  slit. 

Fig.  11  is  a  view  of  the  PA-79  phototube  amplifier,  with  the 
housing  removed  and  the  radio trons  in  place.  This  amplifier  is  of 
the  same  size  as  the  microphone  amplifier.  The  output  and  power 
connections  are  made  by  means  of  a  cannon  type  F  plug,  and  the 



RCA-  Z37 



FIG.  11.     Phototube  amplifier  (PA  -79};   cover  removed. 

same  A  and  B  voltages  are  required  for  this  unit  as  for  the  micro- 
phone amplifier.  The  input  is  obtained  from  a  phototube  mounted 
in  the  film  phonograph,  as  mentioned  under  the  description  of  that 
unit.  The  connection  from  the  film  phonograph  is  made  by  means 
of  a  shielded  cable  2.5  feet  long,  using  cannon  type  P  connectors. 

Fig.  12  is  a  schematic  diagram  of  the  unit.  The  polarizing  voltage 
of  the  phototube  is  supplied  through  a  resistance-capacity  filter 
and  a  50,000-ohm  load  resistor.  The  impedance  of  the  resistor  is 
small  enough  to  prevent  appreciable  high-frequency  losses  when 



[J.  S.  M.  P.  E. 

used  with  the  connecting  cable  mentioned  above.  The  load  re- 
sistor is  capacity-coupled  to  the  grid  of  the  first  RCA-237.  The 
output  of  this  radiotron  is,  in  turn,  resistance-capacity-coupled  to 
a  second  RCA-237.  To  the  output  of  the  latter  is  connected  a 
transformer,  which  adjusts  the  impedance  to  match  a  250-ohm  line. 
All  plate  circuits  are  filtered  by  resistance-capacity  networks,  so 
as  to  prevent  surges  from  the  B  supply  from  entering  the  audio 
circuit.  By  using  radiotrons  of  the  heater  type,  such  surges  in 
the  audio  circuit  due  to  variations  in  the  "A"  supply  are  avoided. 
Curve  1  of  Fig.  13  is  the  frequency  characteristic  of  this  amplifier, 

,5       RCA-257 



FIG.  12.     Schematic  diagram  of  phototube  amplifier  (PA-79\ 

FIG.  13.     Sound  recording  equipment;  frequency  characteristic  of  photo- 
tube and  phototube  amplifier  (PA-79). 

while  curve  2  shows  the  combined  characteristic  of  the  phototube  and 
cable  and  the  phototube  amplifier.  The  combined  characteristic  is 
flat  within  1  decibel,  from  40  to  10,000  cycles. 

Since  the  output  impedance,  frequency  characteristic,  supply 
voltages,  and  means  of  making  connections  are  identical,  this  unit 
may  be  used  interchangeably  or  simultaneously  with  the  microphone 
amplifier.  The  plate  current  of  the  phototube  and  amplifier  is  3.5 
milliamperes,  at  a  supply  voltage  of  180.  The  filament  current  is 
0.6  ampere  obtained  from  an  8- volt  source. 

May,  1933] 




The  remainder  of  the  amplifier  and  control  equipment  is  usually 
mounted  on  a  standard  relay  rack,  as  shown  in  Fig.  14.  However, 
any  or  all  of  these  units  may  be  operated  remotely  from  each  other. 
All  the  units  are  portable,  as  well  as  suitable  for  operation  on  racks. 


The  microphone  distribution  panel  provides  for: 

(1)  Control  of  the  power  supply  to  four  microphone  or  phototube  amplifiers 
with  suitable  protection  for  the  A  and  B  sources. 

(2)  Separation  of  the  audio  and  power  circuits  of  the  four  microphone  or 
phototube  amplifiers,  and  connection  of  their  audio  circuits  to  the  microphone 
mixing  panel. 




TYPE   PA-71 


TYPE.  PA-76 















TYPE    P8-37 


TYPE    PA -76 

TYPE   PB    12 

FIG.   14.     (a)   Front  view  of  recording  rack  equipment;   compartment 
covers  in  place;   (b)  rear  view  of  recording  rack  equipment. 

The  microphone  distribution  panel  is  suitably  constructed  to  be 
mounted  either  on  a  standard  relay  rack  or  on  the  wall.  Fig.  15 
is  a  front  view  of  this  unit.  The  front  panel  contains,  in  order  from 
left  to  right,  a  standard  cannon  type  F  eight-conductor  plug,  through 
which  the  microphone  sound  current  output  is  fed  to  the  microphone 
mixing  panel  and  thence  through  the  compensator  panel  to  the  main 
recording  amplifier;  a  fuse  box;  a  power  switch  for  turning  the 
filament  and  plate  power  on  and  off;  and  another  standard  cannon 
type  F  male  receptacle  through  which  the  filament  and  plate  power 



[J.  S.  M.  P.  E. 

supply  for  the  microphones  is  connected  to  the  power  plug.  This 
latter  connector  may  be  placed  on  the  rear  of  the  panel  if  desired. 
The  fuse  box  contains  the  signal  lamp  and  two  fuses;  a  6-ampere 
fuse  for  the  signal  lamp  and  microphone  filament  circuits;  and  an 
0.5-ampere  fuse  for  the  microphone  plate  circuits.  The  front  cover 
of  the  box  is  hinged,  so  as  to  permit  rapid  inspection  and  replacement 
of  fuses  when  necessary.  A  red  bezel  in  the  fuse  box  cover  is  located 
in  front  of  the  signal  lamp. 





FIG.  15.     Microphone  distribution  panel  (PB-12). 


The  microphone  mixing  panel  provides  for: 

(1)  Control  of  the  individual  audio  outputs  of  four  microphone  or  phototube 
amplifiers,  having  an  output  impedance  of  250  ohms. 

(2)  Control  of  the  combined  output  of  the  four  amplifiers. 

(3)  A  uniform  frequency  response,  from  30  to  10,000  cycles. 

(4)  Control  of  the  frequency  characteristic  of  recorded  speech  so  as  to  prevent 
a  change  in  quality  when  amplified  in  the  theater. 

Referring  to  Fig.  16,  the  audio  inputs  to  the  microphone  mixing 
panel  are  connected  through  terminals  to  the  respective  attenuators 
or  volume  controls.  These  attenuators  are  of  the  bridged  T  type, 
which  make  it  possible  to  maintain  the  impedance  constant  by 
using  only  two  movable  contact  arms  instead  of  three,  as  in  the 
conventional  T  type  of  attenuator.  The  reduction  in  the  number 

May,  1933] 



of  moving  contacts  contributes  largely  to  the  smoothness,  silence, 
and  the  dependability  of  these  controls.  The  series  resistors,  R-6, 
R-7,  R-8,  and  R-9,  in  combination  with  the  attenuator  pads  and  the 
coupling  transformer,  T-l,  provide  a  constant  impedance  for  the  out- 
puts of  the  four  microphone  or  phototube  amplifiers,  as  well  as  a  con- 
stant impedance  at  the  output  terminals  of  the  microphone  mixer. 
Of  course,  if  one  or  more  microphones  are  disconnected  from  the  input 
terminals  of  the  mixer,  it  is  necessary  to  turn  the  attenuator  controls 
to  zero  in  order  to  preserve  the  constant  impedance  relation.  The 

FIG.  16.     Schematic  diagram  of  microphone  mixing  panel  (PB-37). 

loss  of  power  in  the  microphone  mixer  is  only  8.5  decibels  when  all 
the  controls  are  in  the  position  of  maximum  volume. 

In  the  output  circuit  of  the  coupling  transformer  are  connected 
a  volume  control  for  controlling  the  over-all  volume  output  of  the 
mixing  panel,  and  a  compensator  and  three-position  key-switch  for 
introducing  attenuation  at  both  the  low  and  the  extremely  high 
frequencies.  Attenuation  is  required  at  such  frequencies  when 
speech  is  recorded  at  a  normal  level  and  then  reproduced  at  a  higher 
level,  as  is  usually  the  case  in  sound  motion  picture  theaters.  This 
compensation  corrects  for  the  change  in  frequency  response  of  the 
human  ear  with  an  increase  in  sound  intensity;  thereby  making  it 
possible  to  amplify  the  recorded  speech  to  the  desired  level  without 
changing  its  quality.  It  may  be  of  interest  to  note  that  the  com- 



[J.  S.  M.  P.  E. 

pensated  volume  control  as  used  on  radio  receivers  and  phonographs 
has  the  opposite  effect,  at  low  frequencies,  from  that  of  the  speech 
compensator;  however,  no  attenuation  of  the  extremely  high 
frequencies  is  attempted,  since  the  upper  response  frequency  of 
most  radio  receivers  is  4000  or  5000  cycles,  in  which  range  the  char- 
acteristic of  the  ear  does  not  change  greatly.  The  recording  speech 
compensator  provides  for  good  quality  of  reproduction  of  speech 
at  intensities  greater  than  the  original,  as  contrasted  to  the  compen- 
sated volume  control  of  radio  receivers,  which  provides  for  repro- 
ducing music  at  abnormally  low  levels  without  changing  its  quality. 
Fig.  17  shows  the  frequency  characteristics  of  the  microphone 
mixer  for  the  three  positions  of  the  speech  compensator  switch. 
With  this  switch  in  the  center  position,  no  compensation  is  provided, 

30  100  1000  10.00O 

FIG.  17.     Frequency  characteristic  of  microphone  mixer  (PB-37}. 

and  the  response  is  uniform  within  plus  or  minus  0.3  decibel,  at  all 
frequencies  from  30  to  10,000  cycles.  An  attenuation  of  5  decibels 
at  100  and  8000  cycles  is  produced  when  the  switch  is  in  the  upper 
position,  and  of  9  decibels  at  100  cycles  and  5  decibels  at  8000  cycles 
in  the  lower  position.  The  characteristic  obtained  with  the  switch 
in  the  lower  position  is  suitable  for  recording  conversational  speech 
or  dialog,  while  that  with  the  switch  in  the  upper  position  is 
adapted  for  recording  lectures.  The  amplification  system  was  so 
adjusted  that  the  reproduced  output  was  equal  in  volume  to  that 
of  the  original  speech.  The  amplification  of  the  system  was  then 

May,  1933]